Hi Campbell,
After trying various roller systems for my 3m dome, I settled on skateboard bearings onto a rolled steel tube.
Getting the tube rolled (2 of 1/2 circles 5m X 30mm) cost less than $200.
The bearings are mounted onto short pieces of angle aluminium as the picture shows. There are 12 sets.
I can rotate the whole dome with one hand, but usually use two wiper motors to do it.
If you go to
https://homemadeplans5.wixsite.com/lsobservatory
you can see the whole construction story.
I will also be doing a presentation at next years NACAA in Parkes about this style of dome.
Good luck with your project.
Neville
LSO