Free roam

Hello ! I have two female rats Tilly and muffin, I have time for them and they do get out like they should but when they do it’s on my bed because I can trust them to fully roam my room.. I’ve been thinking about it and I’d really like to make an area for them to roam in and out of their cage. Okay let me explain how their cage is, I have a coffee table that their cage sits on top of and I want to be able to open the door and put a ramp down to the floor for them to roam. I was thinking about using a plexiglass gate to put under and around the table for them but everything I’ve been seeing is expensive, even sheets of plexiglass that’d I’d have to put together. Anyway I’ve run out of thoughts any suggestions?