I've never owned rams, but every cichlid I've ever owned except for my tank busters have been raised on flake food. Your rams should eat the tetra food just fine, but you may want to do some research and upgrade on a better quality flake. Look for something that doesn't containe fishmeal as the first ingredient.
Omega One and New Life Spectrum come to mind. You should also consider getting some frozen or freeze dried bloodworms, tubifex worms (my fish all hate the Wardley brand), shrimp pellets, and daphnia (freeze dried is the easiest) for variety in their diet. Your betta will enjoy all these foods also.