O'Driscoll was surprisingly and controversially omitted from the Lions squad to face Australia in Saturday's series decider, with Roberts and fellow Welshman Jonathan Davies being preferred in centre.
With the decision seemingly bringing an end to a storied Lions career for O'Driscoll, Roberts was keen to pay tribute to the 34-year-old.
"The coach picks the team. Warren [Gatland] has picked the team he thinks will go out there and beat Australia on Saturday. That changes week, week out, with injuries and performances," said Roberts.
"Thousands of people have said it before me and thousands of people will say it after me, Brian is one of the most incredible players I have played with or against in rugby union. He will be remembered as a Lions legend, I am sure.
"Brian is a leader, I've tasted that playing alongside him. He's a force, and it is up to me and Jon now to lead the way in midfield and take that responsibility and thrive under the pressure."
O'Driscoll has taken part in four Lions tours since his first in 2001, scoring one try in his eight Test appearances.