I have been plowing and disking my 4 acres for clover for years. I would love to use a roto tiller to get better tillage. I am now reading that a 4 foot roto tiller doesn't work well on 8N's being that the PTO revolution is too fast. Any thoughts?

A neighbor has a NAA with a rototiller. He bought it at Tractor Supply. I was doubtful that it would do the job for the same reason as an 8N. His ground is clay and it worked very well.
I would call and ask him the brand but he had a stroke over new years and I don't want to bother him.

It is the ground speed that is too high, not PTO. If you have an auxiliary transmission like a Sherman that can slow the ground speed, it will also slow the PTO as well, so you are in the same boat. There was a transmission made by Howard that went behind the tractor transmission that slowed the ground speed and did not affect the PTO speed, it had a roto-tiller called roto-vator it was made for. The Howard transmissions are rare and reputedly fragile.

That said, some folks have reported fair to good results using a roto-tiller on an 8N where the soil is light and sandy. Here we have heavy clay and it would likely be a waste of time and money to try.

Howard trans will slow down the rear wheel speed as well as the Everett trans.
Howard also made an offset tiller that bolted to the rear of the tractor around the PTO housing. It utilized a lever that could disengage the tiller as it was raised and lowered. I have two of those in Hillsboro, Ore