Combine peaches, bell pepper, red onion, cilantro, lime juice, garlic, salt, and pepper in a bowl. Set peach salsa aside.

Combine olive oil, brown sugar, Caribbean jerk seasoning, thyme, rosemary, and seasoned salt in a second small bowl. Rub tenderloin with the spice mixture.

Preheat an outdoor grill for medium heat and lightly oil the grate.

Place tenderloin on hot grill and cook covered for 9 to 11 minutes. Turn and grill until tenderloin is slightly pink in the center, 9 to 11 minutes more. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C). Remove from heat, cover, and let sit for 5 minutes before slicing. Serve with peach salsa.