Bosa suffered a groin tear in the first quarter of Sunday's 38-10 loss to the Jacksonville Jaguars.
"It's a tough loss for our defense," safety Derwin James Jr. said. "But it's on us to have his back and hold things down until he gets situated."
Bosa, a four-time Pro Bowl selection, will undergo surgery, but coach Brandon Staley said it's anticipated that he will return this season.
"It's going to be a ways, but we expect him to come back," Staley said. "He's optimistic and ready to attack it. He's in a really good frame of mind. It's never easy when you have an injury like that."
The Chargers are 1-2 as they prepare for back-to-back road games at Houston (0-2-1) and Cleveland (2-1).
"He's ready to play on the edge," Staley said of Rumph, who will line up opposite Khalil Mack.
Staley also emphasized that flexibility and depth were among key motives in the offseason signing of Van Noy, who has the ability to play inside or outside linebacker.
The Bolts also claimed outside linebacker Derrek Tuszka off waivers Tuesday to provide depth.
Bosa has 1.5 sacks in three games this season. He has 59.5 sacks in seven seasons.
At left tackle, Slater tore his left biceps tendon in a loss to the Jaguars, causing him to undergo season-ending surgery.
Salyer, a sixth-round pick, played left tackle in his final two seasons at Georgia, where he helped the Bulldogs win a national championship last January.
"What we're trying to do is keep the sides the same, keep continuity," Staley said. "For us, we feel like that is the best option for us going into this game plan."
"It means a lot to me that my coaches and teammates believe in me enough to give me the opportunity," said Salyer, who becomes the second rookie to start on the line this season, along with right guard Zion Johnson, the 17th overall pick last April.