If you are retrofitting an existing manual (chain) or spring roller shade with a motor, the Rollertrol motors will work fine with a smaller sized shade. And because you are starting with a finished shade it should come with the bottom bar (weight) and all you'd have to do is adhere the fabric to a new tube or fit the motor to the existing tube. What I meant by my quoted excerpt is if you were trying to assemble a shade from component parts, fabric, tube, motor, then you have have more to figure out yourself.
Unfortunately for us DIY folks, motorized shades are still marketed as a luxury item, heck manual window coverings are a luxury item for some. So professionally installed motorization can be a bit pricey, but you typically get a better finished product, installed correctly. It also doesn't have to be overly complex as there have been many tinkerers that have cobbled together their own solution with motorized screwdrivers and drill motors too. When people start looking into the inner workings, the complexity rises from all of the available options between many different motors (size, noise, AC, DC), many different motor controllers, different styles of window coverings (roman, roller, cellular, etc), different fabrics, different tubes and tube adapters, different bracket systems, or headrails for slatted blinds and cellular shades. The concept is relatively simple though, I agree.
So that's why, if you are interested in cellar shades, I suggest it may make more sense to buy motorized cellular shades and find an economical way to get them controlled in Vera. Tubular motors like Rollertrol's typically aren't used with cellular shades and there can be a lot of little parts involved with motorizing your own.