Khan - who stepped up from welterweight to middleweight - was knocked out in the sixth round by the Mexican in their Las Vegas contest, but the British representative has suggested that he wants to return in a major bout before the end of the year.
The Olympic silver medallist has spoken of a potential clash with Pacquiao but Roach, who used to train Khan, has said that his former fighter should take a break from the ring after the manner of his defeat to 'Canelo'
Roach told Boxingscene.com: "That was a real bad knockout. After that kind of knockout, honestly I don't know about [Khan fighting Pacquiao].
"That was a bad knockout and he's going to be under medical suspension for a couple of months, so I don't care what he says about Pacquiao right now.
"After that, I think he should take a break. Pacquiao is a senator now. I think he has one more fight in him but I haven't spoken to him."
Last month, Pacquiao scored a dominant victory over Timothy Bradley.