Former undisputed light-welterweight champion Khan and Roach parted company in the wake of his upset defeat by Danny Garcia in August and the 25-year-old has since appointed Virgil Hunter as his coach.
Speaking in promotion of his fight against Carlos Molina in Los Angeles on December 15, Khan stated that Roach's ability to train was being impaired by his illness.
"It's hard to see him older and getting worse. I wish him the best," he said.
"Freddie, with the Parkinson's disease, he was struggling with instructions and couldn't move as well."
But Khan has used his Twitter account to clarify his comments, stressing he does not hold Roach accountable for his losses to Lamont Peterson and Garcia.
"Hey guys I didn't say @FreddieRoach is a bad trainer, he's 1 of the best out there and took my career to a high winning 2 world titles," Khan said.
"I blame myself for the losses in my career. Not blaming @FreddieRoach or anyone. I just needed a change."
Roach responded by stating his Parkinson's was not the cause of his split from Khan.
"If that was true, why would he say to me fire Manny Pacquiao and Julio Chavez Jr, and they'll keep me? Him, his father, his lawyer and his uncle all said that," he said.
"It had nothing to do with Parkinson's. They know that. And I wish them the best of luck."