Are my trusses capable of carrying the load of insulation and drywall?
Yes, your trusses will support insulation and gypsum board.
The Building Code requires the bottom chord of trusses and ceiling joists to support a minimum of 10 lbs. per square foot. (See IRC Table R301.5)
Gypsum board weighs about 3 lbs. per square foot and insulation (depending on the thickness and type) weighs between .3 and .5 lbs. per square foot per inch thick.
Your trusses were made by a truss manufacturer certified in your state. This requirement is built into their software for the construction of trusses.