It doesn't sound like you've done any of the Adobe-recommended Rotobrush tutorials, which you can find using AE Help.
You really need to do them. Rotobrush isn't the least bit intuitive, there's too much to explain about it in a web post, and we don't understand what you're writing -- you're not using the arcane terminology unique to AE, which is a giveaway clue of a newbie who's trying to take shortcuts to AE success.
Sorry, but it doesn't work that way. You have to pay your dues before you get to the fun stuff.
Thank you Dave for spending your time to feed your needs of showing how superior you are on the subject but my question(s) are pretty simple to understand if you know basic English.
How to change the brush size for MAC? (when it's clearly not working the right way described in the official adobe page) - After Effects Roto Brush, Refine Edge, and Refine Matte
Why when switching to Hand Tool view mode also changes and how to avoid it.
The article which mentions the shortcut is this one:
And to your credit, it is worded wrongly. The correct shortcut is Cmd/Ctrl + left click and drag.
If that still doesn't work for you, you can open up the Brushes panel and change the brush size over there.