The Chargers (8-4) trailed 30-20 with 6:13 remaining and 33-27 with 2:22 left before Rivers brought them back.
Following a pass interference call against Anthony Levine in the end zone, Rivers hit Royal to conclude an 80-yard march to the Chargers' third straight win.
Baltimore (7-5) lost at home in November for the first time since 2009. The Ravens were 11-0 all-time at home against West Coast teams.
Rivers went for 34 for 45 for 383 yards and three touchdowns, two to Keenan Allen.
Joe Flacco threw for two scores for Baltimore, which wasted four field goals from Justin Tucker and 106 yards rushing from Justin Forsett.
Tre Mason scored two long touchdowns and Shaun Hill accounted for three TDs for St. Louis in dominating win.
St. Louis had an out-of-nowhere 38-point first half that tied for second biggest in franchise history. Mason had 113 yards rushing on six carries in the half with an 89-yard score, plus a 35-yard jaunt on a screen pass that opened the scoring. Hill was 12 for 15 for 178 yards and two TDs and ran for a 2-yard score.
The Rams (5-7) scored touchdowns on their first five possessions, got a field goal on the sixth midway through the second quarter to top their previous best scoring total for any game this season. The 38-point halftime lead was the largest in franchise history, one more than against Green Bay in 1980.
The Raiders (1-11) were never competitive and committed five turnovers.
Falcons 29, Cardinals 18
Julio Jones had a career day, catching 10 passes for 189 yards and a touchdown to keep Atlanta in first place.
Arizona (9-3) still leads the NFC West after its second straight loss, but its lead over defending Super Bowl champion Seattle has dwindled to a single game.
More troubling for the Cardinals, they had gone more than 11 quarters without an offensive touchdown until a meaningless score with just over a minute remaining.
Steven Jackson broke off a 55-yard run — his longest run since 2009 — to set up a touchdown on the Falcons' opening possession.
Jones hauled in a 32-yard scoring pass, and Matt Bryant kicked a career-best five field goals for the Falcons (5-7), who matched New Orleans' 35-32 win at Pittsburgh to remain tied for the top spot in the NFC South.
Drew Brees threw five touchdowns for the ninth time in his career as New Orleans took advantage of a mistake-prone Pittsburgh team.
Kenny Stills caught five passes for a career-high 162 yards and a score as the Saints (5-7) ended a three-game losing streak by restoring a little bit of respectability and a sense of order to the NFC South.
The Steelers (7-5) kept New Orleans tight end Jimmy Graham without a catch, but it hardly mattered. Brees worked Pittsburgh's secondary over anyway. Ben Watson, Marques Colston, Erik Loring and Nick Toon hauled in touchdowns as New Orleans romped.
Ben Roethlisberger passed for 435 yards and two touchdowns, but also threw two interceptions for the Steelers.
Orton put the Bills ahead 7-3 with 8:04 left with a 3-yard pass to Chris Hogan. Buffalo's defense scored on the next play from scrimmage, when Hughes stripped the ball from running back Terrence West, and returned the fumble 18 yards for a score.
It was too deep of a hole for Browns rookie quarterback Johnny Manziel to dig out of. Taking over with 12:01 left after starter Brian Hoyer threw his second interception, Manziel capped an eight-play 80-yard drive with a 10-yard touchdown run that cut Buffalo's lead to 20-10.
The Bills (7-5) won their second straight. Cleveland (7-5) lost for only the second time in six games.
Josh Scobee kicked a 33-yard field goal with 28 seconds remaining as Jacksonville rallied from a 21-point deficit to win.
The Jaguars (2-10) ended a four-game losing streak and dealt the Giants (3-9) a seventh consecutive loss that could raise more questions about coach Tom Coughlin's future.
The Giants dominated the first half, scoring 21 points in the second quarter and looking like they would notch their first victory since early October.
Rookie Aaron Colvin returned a fumble 41 yards for a touchdown in the fourth. It was the first time in franchise history that Jacksonville scored two defensive touchdowns in the same game.
Dalton shrugged off three first-half interceptions to help the Bengals (8-3-1) win on the road for the third consecutive week, a franchise first.
Cincinnati leads the tightest division race in the NFL, beginning the day with a half-game edge over each of its AFC North rivals. Tampa Bay (2-10) threatened in the closing minutes, however a 21-yard completion that would have put them in field goal range was wiped out after a replay review confirmed the Bucs had 12 men on the field.
Dalton ran for a 5-yard TD in the second quarter, then threw 13 yards to Green to put the Bengals ahead 14-10 late in the third.
Fitzpatrick returned to the lineup after being benched for two games for Ryan Mallett, who suffered a season-ending chest injury last week.
J.J. Watt helped out in the win, too. He had his third touchdown reception, two sacks, forced and recovered a fumble for Houston (6-6).
Tennessee's Zach Mettenberger injured his right shoulder playing behind a makeshift offensive line missing three starters. Jake Locker took over in the third quarter and threw for 91 yards with a touchdown and two interceptions for the Titans (2-10), who have lost six straight.
Andrew Luck threw a career-high five touchdown passes and topped the 300-yard mark for a franchise-record 10th time this season, leading Indianapolis past Washington.
Indianapolis (8-4) won for the eighth time in 10 games since starting 0-2.
Luck was 19 of 27 for 370 yards and had TD passes of 30, 3, 48, 73 and 79 yards. He broke Peyton Manning's mark for most 300-yard games in one season and joined Manning and Dan Marino as the only quarterbacks to top 4,000 yards in two of their first three seasons.
He did all that while Robert Griffin III, the No. 2 overall pick behind Luck in 2012, watched from the sideline. Griffin's replacement, Colt McCoy, was 31 of 47 for a career-best 392 yards and three TDs, also a career high. Washington (3-9) has lost four straight.
Vikings 31, Panthers 13
Adam Thielen and Everson Griffen each returned blocked punts by Minnesota for touchdowns, the fifth time in league history one team had two in the same game, and the Vikings handed Carolina its sixth straight loss.
Despite entering the week just a half-game out of first place in the struggling NFC South, the Panthers (3-8-1) again stumbled out of their bye. They're 0-4 under coach Ron Rivera following the annual in-season week off.
This was the seventh-coldest game in Vikings history, with a kickoff temperature of 12 degrees. They're playing outside this year for the first time since 1981.