It would be good to know what type of trusses you are using.
In most cases there is plenty of room in the truss cavity to pile up blown-in insulation. This can be cellulose (fire treated) fiberglass or several other materials. There is probably a local material in your area that is the most cost-effective for blown in insulation. The best way to find out is to get some bids.
Most blow in insulations are designed for relatively flat ceilings. If you have some steep slopes you might consider my favorite general insulation system BIBS - the blown in batt system. This is not available everywhere.
The link below is to one installer. You can check the web or locally to see if you have this available where you live.
Very effective insulation that only cost me about 10% more than fiberglass to install. The energy upgrade is more like 20-25%.
Link:
http://carrollinsul.com/b_i_b_s.htm
