Combine first 4 ingredients in a 6-quart pressure cooker. Bring to a boil; reduce heat, and simmer 5 minutes. Remove 1/2 cup of chili sauce mixture from pressure cooker.
Trim fat from brisket. Cut brisket in half crosswise. Rub the brisket with pepper and garlic. Place in pressure cooker. Spoon 1/2 cup chili sauce mixture over brisket. Close lid securely; bring to high pressure over high heat (about 5 minutes). Adjust the heat to medium or level needed to maintain high pressure; cook 1 hour. Remove from heat; place pressure cooker under cold running water.
Remove lid. Remove brisket from pressure cooker, and set aside. Add the brown sugar to chili sauce mixture in pressure cooker; bring to a boil. Reduce heat, and simmer, uncovered, for 5 minutes, stirring frequently.
Shred the brisket using 2 forks. Return meat to sauce in pressure cooker; cook until thoroughly heated. Spoon 1 cup meat with sauce over bottom of each roll, and cover with tops of rolls.