On Roll20, the jpg version of the pyramid roof will work perfectly. It will be easy to drag & drop it onto the base map and delete it when the players go inside.

I will be letting the author, Jeff, know that I am running his game, but since it is a Virtual Con this year he will only see it if he logs onto my Roll20 game. Also, Alyssa Fadden is the cartographer who made the City of Gaxmoor map that this came from. She was one of the guests of honor at last year's Total Con. I don't know if she will be at the virtual version this year or not. She did a great job with the City map. I can't post the whole map as it is a commercial product of Troll Lord Games & Luke Gygax, but here is a little larger clip to show off more of her work.
Gaxmoor-Clip.JPG