Is there a relationship between slightly elevated liver enzymes and roux-en-y gastric bypass surgery?

Not really: It depends on which enzymes are elevated. Some elevations can suggest gallstones, which can happen to anyone after profound weight loss. Other elevations may suggest inherent liver problems. Elevations in of themselves generally are not directly related to surgery.

Not directly related: Having morbid obesity puts the liver at risk for fat accumulation. When it has enough fat the liver may become inflamed and have enzyme elevations. Also rapid weight loss after bypass surgery can cause gallstones to form. When the gallstones leave the gallbladder they can get stuck in the tubes between the liver and intestine. That can cause liver inflammation too.

NAFLD: Very well may be fatty liver disease and it is not too uncommon to detect an increase in lfts after rapid at loss.

Most likely: Related to fatty liver or gallstones.