under roundhouse is patched im afraid , however, you can get out of makin with a bayonet jump or a hard rpg bounce, and its also possible to get out of asylum with 2 rpgs. The hardest is probably hangar, because unless you have a friend you have to do some tough bounces to get out of hangar.
Yeah there is another way under roundhouse, you should watch ngu glitch crews videos, they are mostly tuts. u get under by S& spawn point when defending.