Roberts was a surprise omission from the side beaten at Brentford last month as Smith attempted to halt their recent slump.
But the defender won his place back and was back to his best as Boro ended their six-game losing streak with a 1-0 win over the Bees on Tuesday night.
"I came into bundles of criticism for leaving him out but since he has come back into the side, even though the results haven't always gone our way, he has looked an absolute colossus at the back there," said Smith.
"If there is anybody who is going to drive us on and keep us moving in the right direction then he is going to offer that."
