I wouldn’t have wanted to do that, either.
I’m very glad you felt comfortable saying, ‘no.’
I like fkm suggestion to explore your uncomfortable feelings around it.

Can you ask him again to explain how that was supposed to help you?
Maybe he was trying to help you feel in control. Maybe he suggested the role-play to see what feelings came up? I can imagine there would be quite a few!
I think it’s important to tell him that just considering it brought up a lot of feelings.

A previous therapist wanted to help me get in touch with my anger one time. She brought out bataccas (soft bats) and invited me to hit her with them. I couldn’t do it. Then she suggested I hit the chair role playing it was the abuser. I couldn’t do it then, I might be able to do it now.

Hopefully, your therapist had something like this n mind.