Originally Posted by Tom Stormcrowe

A lot of old school tourists did it with rear panniers only in the 70's. That used to be how it was done. There can be some handling issues that way though. It also really restricts you weight wise, but that's not necessarily a bad thing.

You might look at a frame bag as well, to allow for a bit more carrying capacity.

Something like this:
http://www.jandd.com/detail.asp?PRODUCT_ID=FFP

As to the trailer and rough terrain? Remember, I pulled a heavy trailer across the fire roads up in Michigan in sandy conditions with a road touring bike.