I have been asked by a DBA, if we can backup reportservertempdb, why not!
Here is the answer:
We should backup the database reportservertempdb as we backup the reportserver.
The reason to backup the reportservertempdb is to avoid having to recreate it if there is a hardware failure. In the event of hardware failure, it is not necessary to recover the data in reportservertempdb, but you do need the table structure.
If you lose reportservertempdb, the only way to get it back is to recreate the report server database. If you recreate the reportservertempdb, it is important that it have the same name as the primary report server database.