You mentioned you want to revert an entire workspace... Just to clear up what you're asking:
Changes are checked-in to a repository workspace.
Checked-in changes are delivered to a stream.
Differing from some SCM systems in that there is a two step process.
Do you want to revert to a prior state in your workspace? or the steam?
Reverting a changeset delivered to a stream is easy, IBM actually has some decent doco on it.
If you checked in a change to your workspace but didn't deliver... it's going to be rougher, best you can hope for is restoring from local history in your IDE. The repository workspace doesn't store history.