Roos, 32, was a second-round pick out of Eastern Washington in 2005. He played five games in 2014 before suffering a season-ending knee injury.
"Michael was such an intelligent football player," said Steelers offensive line coach Mike Munchak, who was in the same post with the Titans and helped the team decide to draft him.
"He always understood his opponent, our offensive scheme, their defensive scheme and all the angles involved. That knowledge and film work let him play with a great deal of confidence. ... As coaches, we were never concerned about his matchup, because he could handle any opponent, whether it was a big guy or an athletic guy."
Roos played his rookie season at right tackle, then moved to the left side. In his first nine seasons, he missed just one game, after an emergency appendectomy in 2012.
The Titans used the 11th pick in the 2014 draft on left tackle Taylor Lewan as Roos entered the final year of his contract.
Roos' injury resulted in OATS surgery, which stands for Osteoarticular Transfer System.
"A piece of bone came loose, so they cleaned that out and drilled new holes, new bone out of my knee to fill that hole," Roos said.
Roos said in late December that he was seriously considering retirement, and that the mental drain of his 10 seasons also was a big factor.
The Titans plan to go forward with Lewan as their left tackle. Their 2014 right tackle, Michael Oher, was recently cut, and they need a replacement.