What do I need to get a line level signal from a Roland R-44 into an AG-AC160A? Is the only route in through the XLR mike inputs, set to line level? If I just want a good quality mono feeding into the camcorder is this the way to do it?

The R-44 only has line outputs on RCAs, so you'll need an RCA to XLR cable. They're not hard to make, and they're cheap to buy. You might also want to get a dual RCA to single RCA y-cable, to combine the signals into one mono signal.