Preheat oven to 375 degrees F. Spray two standard muffin tins with cooking spray and set aside.In a small saucepan, combine grape jelly and barbecue sauce. Cook over medium-low heat for 10-15 minutes, whisking occasionally until no lumps remain and sauce is smooth.While sauce is cooking, remove crescent rolls from packaging and form into 4 rectangle shapes. Press the seams together with your fingertips to seal. Take a knife and cut each large rectangle into 4 smaller ones. After you have cut all of them, you should have 16 smaller rectangles.Press each small rectangle into the prepared cups of your muffin tins. Press firmly into the bottom and up the sides, stretching the dough a bit as you go. Place a frozen meatball in each cup.Top each meatball with 1 Tablespoon of the sauce. Bake in the oven for 12-15 minutes, until meatballs are cooked through and sauce is bubbly. Top with sliced green onions and enjoy!