It is extremely important for rats to have enrichment in their environments! Rats are highly intelligent animals and need things to keep them busy. Rats need at least 2 hours a day outside of their cage in a large, safe, play area. No animals are meant to be in a cage their whole lives! There are many playpens that can be purchased online or you can make your own! Out of cage time/free roam time is a great time for training(yes, rats can learn tricks!), bonding and exercising!
*Photos from google credit to the owners*
It is also important for their cage to be enriching! They will spend the majority of their time in their cage, so they need a lot of things to do and places to sleep. Fun things to add are hammocks, baskets, boxes, ropes, foraging toys, chew toys, tubes/tunnels, dig box, hides, wooden ladders, lava ledges, wooden ledges, appropriately sized wheel, and the list could go on! These items in their cage should be moved around and/or switched out for other things every 5-7 days so that they do not become bored.