The move was announced before Friday night's game at Tampa Bay. Right-hander Evan Reed was optioned to Toledo.
Rondon went 1-1 with 14 saves in 30 games with Toledo.
"He's not being brought back as a closer," Tigers manager Jim Leyland said. "Sixth, seventh, sometimes eighth (inning) maybe, depending on who's available. It's very rare that guys that young are brought up as the closer."
"I don't think he's a totally finished product yet but I think he's made a tremendous amount of progress," Leyland added. "He's throwing pitches for strikes and he's throwing strike one, and he's worked on (shortening) his delivery."
Leyland said Joaquin Benoit will get most save opportunties.
"Hopefully we'll get settled into some kind of order now with Benoit getting most of the calls if he's available," Leyland said.