he had some good roles as long as someone writes a script for him
You kidding? Mork and Mindy was an improv showcase for Williams. I remember reading while the show was still on the air that sometimes the script just read: Mork enters, and he was on his own. Pam Dawber was giving a cue line to break in with when the craziness got out of hand, so they could get back to the script.
Actually Good Morning Vietnam all his lines on the radio were improvised. They basically said “Go for it”. And he did.
I watched an HBO standup of Robin one time, looking forward to many laughs. But he over loaded his shtick with F-this and F-that so much, I switched channels.
You really don't know anything about Robin Williams, do you? That's a rhetorical question. Do you know what that is?