1. Stir together first 3 ingredients in a medium saucepan. Bring to a boil over medium-high heat; reduce heat to low, and simmer, stirring occasionally, 25 to 30 minutes.
2. Cut rolls vertically through top, cutting to but not through bottom. Place 2 meatballs in each roll. Top with desired amount of relish.
Note: For testing purposes only, we used Wickles Hoagie & Sub Sandwich Relish.
To make ahead: Prepare meatballs as directed through Step 1. Store in an airtight container in refrigerator 3 to 4 days.