Lauch Game without the VTT?

1 of the groups I am in has been using Roll20 for a while for just the character sheets for a while. Is there an option to launch the game without the VTT at all? This is a lot of overhead that could be skipped.

I don'y believe so, and that would be pretty weird - roll20 is the VTT first, and character sheets and other stuff are additions on top of it.

Couldn't the players use the mobile app for just character sheets?

I run my Trail of Cthulhu campaign just for the Character Sheets, so I just have a Start Page. It’s green, like a green baize pinboard, and it has PC portraits on it, and NPC portraits are shown, etc.,  We use nothing else, no Tracker, no Tokens, no Battle Maps, etc., 

Not yet. I believe that other sheets are due to follow the pioneering of the Marvel sheet, which can be built and referenced outside of the VTT.

The Character Vault has been updated to allow creation and viewing of character sheets outside the VTT.  Keith is correct -- we started with Marvel Multiverse RPG, and more sheets to come!

Still would be cool to be able to "Hide" the VTT... or at least to get the Character Sheet full screen on top of the VTT instead of just floating... An important part of the game can be theater of the mind, where user needs just the character sheet, chat and compendium, so user needs the right bar, and the character sheet... Popping out the sheet is not satisfactory because all dialogs (pop ups, and chat messages) are still in the other tab of the browser where the VTT is...