I don't know in term of performance but Tyson would have been quieter for a longer period of time, possibly staying out of the big troubles for an extended lapse of time.
I think Wlad could have been more or less as good with Roach as Freddie doesn't train all his fighters the same way, he would have spotted Wlad's weaknesses and strengths and adjust in consequence. I can't say he would have done a job as good as Manny but it would have been, in my opinion, a very great job indeed, if the chemistry would have been ok between the two, of course.