You are correct that there are not multiple speaker outputs on the 1050 (like the A/B outputs on some receivers). It can still be done, however -- but it will require some extra hardware. (I've thought about doing something similar a couple of times before, but never actually done it.)
1) You could use a speaker switch box -- wire from the 1050's main speaker outputs to the switch's inputs and connect your main speakers and patio speakers to the outputs.
2) You could use the 1050's internal amp for the main speakers and use a separate amp or receiver hooked up to an output from the 1050 to drive the patio speakers (I haven't done this, so I'm not sure which would be better -- the preamp outs or the tape monitor outs...).