Rose is a beautiful lake. I've never paddled it but have seen it from above while on a day trip. I'm not sure about Rose but Duncan has Lake trout which should be reasonably shallow at the time of your trip.
Be sure and make time for a meal at The Trail Center, excellent food.
I would probably take the 5wt and the 8wt. You are going to be throwing large flies,long casts and possibly dealing with wind while casting.
I would not hesitate to use 2 to 3 inch long flies be they leech patterns,clouser minnows or even wooly buggers.
There is a wealth of info at www.bwca.com
and very nice and helpful people on the message board.
Are you using an outfittter ? If so which one ?