Heat a griddle or a large skillet over medium heat, add olive oil.
Add the onions and bell pepper and cook, stirring, about 6 to 8 minutes.
Add the garlic and cook for about 30 seconds.
Then, push the mixture off to one side of the griddle. (Remove vegetables to a plate if using a skillet.)
Add the meat to the hot part of the griddle.
Cook, keeping it moving, until the meat is not pink, about 2 minutes.
Mix the meat and the onions and bell pepper together.
Add salt and pepper to taste.
Top with the meat and veggies with the cheese to melt on the griddle.
Slice the rolls lengthwise, fold them open, and spread with butter. If desired, lay them flat on the griddle to toast them a bit.
Divide the meat and cheese into 4 sections.
Slide a spatula under a section, and transfer it onto a roll.
Serve hot and melty.