It can be rough getting spots in programs at MedStar. I had a child who did their Learn to Play at MedStar, as soon as they were ready for organized hockey we tried to sign them up and everything was full. I'd suggest you give it a go though since parents I've spoken to who have done Rooftop Hockey have had great things to say about the league and the coaches.
If you don't get a spot there's other great options in the area though.
The ST James (Springfield) also has a decent house program that is very similar to Rooftop Hockey.
The NoVA Ice Dogs (Mt. Vernon) have a great rec program that participates in the CCHL (Capital Corridor Hockey League). So instead of playing against the same kids every week, you go to other local rinks and play against rec level teams there. A lot of kids actually like this format better.
I listed the 2 closer programs to Medstar, but here's a link to all the CCHL member club programs.
https://www.capitalcorridorhl.org/about/cchl-member-clubs/44245