Start with cutting the nightcrawlers into 3 or 4 pieces and every couple feedings make the pieces bigger and bigger untill you have him up to whole ones. As for roaches people typically use B. Dubia Roaches. They can be a good feeder for your frog if he likes them, some frogs(like mine) are picky and don't care for them, and I've heard it's most likely due to their spikey legs, some frogs don't like them but some get over it and gobble them up. Also just like crickets roaches should be gut loaded before feeding them to your frog