A whole slew of other roads exist east of Hwy11 especially as you move further east. Very close to Huntsville and just south of Algonquin park you will find:
For some Huntsville backroads, #9, #10, #2, are all just east and south of Huntsville and make for a good loop
Hwy35 South of Dorset, this road is excellent with awesome super smooth pavement - a very scenic ride with fast sweepers and some amazing scenery.
Kushog Lake Rd - Lot's of twists, hills and a few blind corners thrown in for good measure - very close to Carnarvon off Hwy35.
Harburn Rd #19 to #14 as a loop off Hwy118 - can get quite technical in some parts lots of great twisty, hilly bits.
Kenisis Lake Rd and Watts Trail - Kenisis Lake Rd is an out 'n back, but adding in Watts Trail (which loops around a lake) makes it a very technical run. There can be sand on Watts Trail very late in the season since it has little traffic, but it's one of the most twisty roads I have been on in Ontario.
North of Peterborough area up towards Algonquin you can ride:
Hwy507 - runs north/south between Buckhorn and Gooderham - very fast sweepers and decent pavement
Glamorgan Rd aka Buckhorn Rd #3 - connects nicely with the Hwy507 between the Hwy503 and the Hwy118
Hwy118 - nice smooth curves and rolling scenery, with a sweet section around Loon Lake
Essonville Line #4 - a good route to connect between #118 just east of Loon Lake and Wilberforce with nice pavement and some nice twisty bits
Elephant Lake Rd / Peterson Rd - if this road is clean you won't be disappointed. Runs between Maynooth and Harcourt
Hwy60 - a slow meandering run through Algonquin Park. Nice scenery. A great place to stop for a break between the great roads on either side of the park.
There are also some nice roads up near Barry's Bay and south/east, including Old Barry's Bay Road, Siberia/Kartuzy Road, Opeongo Road, Hwy's #512 and #515
Further south and east towards Calabogie you find Hwy's #511, #508, #509, Buckshot Lake Rd and much more - all excellent roads much further east and usually coming from Toronto this turns into a 1000km day of frost heaved fun.
Ride safe and enjoy!