Advice on Client PC / Laptop Backups

we use roaming profiles therefore all work is on the server by default or at least replicated when the user logs off

The server is backed up via backup exec to tape and NAS

Use BE's DLO to backup client's/user's data to a server's location. If you have enough room on your tapes, make a backup of this location on tape too.
When BE is available (such as your scenario) this is the preferred method.

Where I administer, we indeed have the rare case that the client pcs are that important. We have programmers, software developers, CAD designers, people running mathematical simulators - in total: all very, very fat clients. That's the only situation where I would ever consider backing up clients: if reinstalling those and reconfiguring is consuming a lot of time and cannot be automated that easy. So please respect Leew's advice, he's right.

What we take to (image-)backup our clients' c: drives (data is at the server, c: is just full of installed software) is drive snapshot ("DS"). DS is a simple, command line drive, easy to automate (via task scheduler) cheap and reliable imaging software. We could have used windows' internal backup, but the compression it uses did not meet what we needed to save space/bandwidth.