If you want to continue using UVB, I'd recommend using a calcium supplement without D3 as too much will cause calcium overdosing. Excess calcium is just as bad as too little. Make sure you're supplementing with vitamins too. UV bulbs should be on about 8-10 hours a day, although it can vary greatly between species. UVB isn't usually used for toads and frogs as many species spend most of their day hiding or perching in places which are shaded from the light. Replace the UVB roughly every six months if you decide to continue using it. I'd recommend a ReptiSun brand bulb like this when whenever you replace it next: 
https://www.amazon.com/Zoo-Med-25156.../dp/B00A8RI8TK
Neither crickets nor mealworms naturally have a lot of nutrition, which is why we supplement our herps with calcium and vitamins in the first place. Roach nymphs are actually very small. I've fed young roaches to American toads before with no issues. The rule of thumb is to feed frogs a food item which is about the same length as the distance between their eyes. They are hard to find in most pet stores so I recommend ordering them online. You can get them shipped directly to you door by various websites, even Amazon if you really want to (although this is generally more expensive). By gut loading, I don't necessarily mean you have to raise them from the start. Just make sure you give them food coated in calcium and vitamins the day before feeding, so they contain a lot of nutrition. 
Even though you don't see the toads move much, that doesn't mean they don't want to every once in awhile. As long as they are both males (males are smaller than females, ranging about 2-3 inches in California toads, which are a subspecies of western toads) they could likely be maintained in a smaller tank. Just make sure you give them lots of room to burrow as they will utilize as much bedding as you give them. Every once in a while, my toad Herbert will bury himself in the most random spot and I'll be stuck looking for him for 10 minutes just in order to feed him, lol.