Split the rolls lengthways across the top taking care not to slice all the way through.
BBQ the sausages/frankfurters over a medium heat, browning on all sides until cooked through (approximately 10-12 minutes for sausages, less for frankfurters).
On the hotplate or in a pan on the BBQ, fry the onions and peppers with the olive oil and balsamic vinegar until soft.
Warm the rolls on the BBQ rack (or for a few minutes in a low heat oven).
Open up the roll, add a squirt of sauce, add a sausage/frankfurter and top with onions and peppers.
Notes
For a variation, grill corn on the cob, slice off the kernels and add them to the hotdog topping. Or try fried mushrooms instead of peppers.