Possible Clues:

• Bit of bun flavoring
• One might be on a roll
• I'm on a roll!
• Bun topper
• It might be on a roll
• Bit on a bun
• Burger bun tidbit
• Identical starts to serious epidemics overshadowed by germ produced by oil producer
• Hamburger bun topper
• Oil producer having word with open tennis star?