UPDATES TO FOLLOW
2 Sets of Roller Blades (16 wheels/32 ball bearings) from Goodwill
Meade motorized telescope arm
Some sort of metal rail
I usually move the dolly by hand but for time lapse or slow movement I use a parallax continuous rotation servo that winds fishing line through a pulley attached to the dolly and onto a small spindle. I control the servo via a Traxxas (for a remote control car) controller and receiver. The Traxxas controller has a potentiometer on it that allows speed control of the servo in both directions. An easier option would be a rotisserie motor - I found one at Goodwill but didn't wind up using it cause I wanted to go wireless.
Give credit where credit is due, this project is a remix of these two projects:
DIY video & timelaps electrical dolly
DIY Inexpensive Camera Slider