Not an official answer, but based on what I've seen as a Forum regular, YouTube watcher, and Kickstarter lurker, Yes you can do that. There is a "Contact Us" link at the bottom of Roll20 webpage(s), if you want to send a direct message to inquire. There are limitations on how you can use the Roll20 Logo, of course. There could be limits if you're using other artists' art (maps) in your roll20 screenshots. You might need permission from each artist. To the extent that the Art/Maps shown in your screenshot is your own created assets, and the roll20 Logo is not used, yeah I'm pretty confident that you can show the Roll20 tabletop interface in your ads (the zoom slider, the toolbar buttons, the page environment being used with your art-assets). There is not any limit on your speech/pitch to say "Works well with Roll20", that's absolutely fine to post.
