If your rats like and eat the Oxbow, awesome. We have not had that luck. A couple of our boys refused to eat it unless they were utterly ravenous, and lost weight while on it. We switched to Harlan Teklad blocks, and they regained the lost weight. Even folks who’ve refused other blocks have liked the HT stuff.
A variety of fresh fruits and vegetables is an important part of their diet. There should be a thread kicking around with a list of what’s safe for rats, what should be fed with caution, and what to avoid. There are a lot of things they can have. Ours enjoy broccoli, cooked peas and corn, cucumber, avocado, strawberries, blueberries, banana, noodles (cooked or dry), raw unsalted pumpkin seeds, puffed grain (kamut is a favourite), cooked sweet potato, boiled egg, and the occasional bit of chicken or turkey at holidays. Rats are opportunistic omnivores; not everyone chooses to give their fuzzies animal products, and not all rats will like them equally, but you can give them some on occasion if that’s how you roll.
It’s a good idea to avoid highly-processed human food, or snacks with added sugar and salt. A little bit of cracker or potato chip once in a great while is probably fine (provided it doesn’t contain anything else that might be unsafe for them) but shouldn’t become a habit. My mother once knew a guy with a rat named Spiffy Horace, and he allowed Horace to share his beer. The wee guy seemed to suffer no ill effects, but it’s not something I’d recommend. Same goes for sharing carbonated beverages with them. Rats can’t burp, but their farts can peel paint.
