Everyone knows about the roll cast but does everyone know about the Tongariro roll cast?
The kiwis have invented some good things for us, jetboats and commercial bungy to name a few and whilst they might not have invented this one the name has stuck. The key is the line slipping before the final delivery. Give it a shot! Once you've practised a few times you'll see there's nothing different to most of the little spey tips and tricks you probably already know, perry pokes, circle casts and so on.
The other somewhat obvious but easily overlooked trick with tight spaces is to change your gear. If you carry a short shooting head (at least in principle if not a fully blown shooting head) you might just be carrying a get out of jail free card that could be worth its weight in gold when you only have roll cast space but need a bit of distance.
Also don’t be scared to shorten up that leader – do you really need 18 feet? How about learning to cast with the other hand, sometimes that helps too!