It's very unlikely that there is Dolly Varden in Rolley lake even if they're listed on sites like Fish Wizard. I have fished Rolley several times and have used flies which would normally tempt Dollies and never once have I ever heard of anyone pulling anything except the stand 10-12" stocked rainbow out of there. Sounds more like a case of mistaken identity though I'm not saying it's impossible.
If it's Dollies you want, you'd be much better off sticking to Squamish.
I'm sure there's a lunker or two hidden in the depths of Rolley although tempting them to take your fly is quite another story. They're that large for a reason and surviving into a third season is quite an accomplishment in such a lake which receives so much pressure.
There are certainly a tonne of Crappies in Whonnock. Most are on the smaller side but they put up a valiant fight. Be sure to be gentle with the little paper-mouths as you can tear the lips right off 'em if you're not careful.
We go to Rolley alot in the spring to camp, it's not far away and we can get thier quickly after work. I usually spend my days there floating around in my tube with my 5wt. I have had some strikes that have just about ripped the rod out of my hands just to have my 3X tippet broken off. Early in the season you can get some nice size fish on the far side of the lake, before the big ones go deep. I have battled Walter once on Rolley, but he is a sly old fish. After hooking him he headed striaght for a snag and broke off. It was a brief fight but a good one.