I’m working in a multi-user environment and one of the other developers made some unneccessary changes…is there a way to undo them?

Yes. There is a rollback function that allows you to effectively create a new version of the files using previous versions.

Ex. The changes were made in version 10 when you rollback to a previous version is will simply create a new version (v. 11) using the state of the file from the version you picked (rolling back to v. 7 will create v. 11 that is identical to v. 7)