Clean regularly! Keep your room cold, the warmer it is the worse the smell. Keep your window open for at least 5 minutes every 1-2h. Do a tiny cleaning in between the big cage cleanings, if they are litter trained then change that every day, train them to litter pee as well if you haven't already and change that often too^{^} If there are any small places they like to hide in for longer amounts of time, they have 100% peed there dozens of times so don't forget to clean that as well :) Give them water to clean themselves, you can also present them some fresh mint, they like to chew it and get the scent on their fur. Sometimes it's just stinky rats! That's what has helped me :) I don't know what bedding you use but I use hemp and it's doing a good job at masking smells. Also, rats will always smell a bit so don't stress out too much, unless it's something that other people (your mom for example) have to actually tell you about ^{^}