Set your grill to about medium heat and brush the grates until they are clean.
To make the rosemary-infused bbq sauce, whisk the ketchup, butter, Worteceshire sauce, maple syrup, chili powder and rosemary in a small saucepot.
Heat the rosemary-infused sauce over a medium-high flame; once it is boiling, decrease the heat to medium-low and cook it for 5-7 minutes, periodically stirring until it thickens up.
Whisk the kosher salt, pepper, lemon pepper, smoked paprika, cayenne pepper, garlic powder, and onion powder in a small bowl.
Pat the chicken wing drummettes dry with paper towels and place them into a large bowl.
Add the olive oil to the chicken wing drummettes, toss to coat, then generously apply the seasoning blend and toss to combine.
Place the wings onto the grill in an even layer, cover them and cook for 30 minutes.
Baste the chicken wings with the rosemary-infused bbq sauce, place the lid back onto the grill, and cook for another 30 minutes.
Continue to baste the wings with the sauce until they are slightly charred and reach your preferred doneness.
Toss the chicken wing drummettes with any remaining rosemary-infused bbq sauce.
Serve and enjoy!