Highway 155 to and from La Tuque has a constant shoulder except for 2.3km southbound. Traffic is fairly heavy with some trucks but I think it's worth riding. I know I will go back. I've never been north of La Tuque and understand there's no shoulder, more logging trucks cutting corners. I have no desire to ride there.
A short text (click the the flag on top if it comes up in French):
http://www.borealphoto.com/gallery/4440564_xcfbN
Some photos:
http://www.borealphoto.com/gallery/3686833_yJrDp
La Mauricie park is a nice ride too. No roof there obviously but you can ride through in a day. You can cross the river on a shuttle boat in St-Jean-des-Piles.
Both highway 170-172 on the Saguenay are nice too. Shoulders come and go and traffic is moslty mild except for a stretch between a pulp mill west of Cap Jaseux and Chicoutimi where traffic was pretty high with no shoulder.
The 172 is isolated with few services. Ste-Rose-du-Nord is a beautiful village with all services.
Cap Jaseux has cabins. No RVs there because of the 20% grade access road.
Villages are evenly spread out on highway 170. It's hilly but there's usually a shoulder going uphill.
Photos of highway 170 and 172:
http://www.borealphoto.com/gallery/3779204_x8dFn