Pork loin is just so lean, it really needs something fatty to help carry that flavor, imho.
I stuff with a mix of pepper jack cheese (have been contemplating trying a very sharp cheddar as well) and sliced cubes of pepperoni.
The flavor is top notch, but I sometimes have problems with presentation. As the loin tightens up, the cheese/oil from the pepperoni need somewhere to go, and loin isn't exactly the most porous meat on the planet. I usually make "weep holes" on the top, so the oil comes out, and mixes with the rub, hardening up into flavorful stripes on the exterior. I haven't tried a looser roll, with some space in there for the sauce to collect, but that might not be much better.
D