Jeff's Map puts Rosebary to Shippagew at about 10 hours. I'll be able to give you a first-hand report of the stretch from Rosebary to Shah when I get back in a week and a half, but my initial reaction is that it's probably more than you should take on, at least as a one-day trip. Book one of the campsites along the Tim (or spend a night on Shah) and take two days getting to Shippagew. 

Return-wise, I'd suggest not going straight back up the Tim. While there won't be any significant current to speak of, you'll still be going upstream, you'll definitely have to pull over every beaver dam, and besides, it's no fun going back the way you came. Make a loop of it by going back through Big Trout, White Trout and up the Petawawa to Misty. From there you have a few options to get back to Rosebary and head out. 

Or if that's going to make it a longer trip that you planned on, consider only taking the Tim as far as Shah and then looping back around through Misty as well. 

If moose is what you're after I highly recommend starting at Magnetewan and going through Daisy and staying on Misty for your first night, Grassy Bay for your second night (down the Petewawa), Macintosh for your third night then you can either go back the way you came in from or you can go through Muslim, Wenona, Bandit etc and back up through Rain/Casey's if you want. I did a similar route a few weeks back and lost count of Moose at 15!
I sent you a private message, by the way. ;-)