Can you space trusses more than 24" on center if you use 4x4s or 6x6s for the lumber instead of 2x6s?
Timber frame trusses (and steel frame trusses, for that matter) are frequently spaced wider.
Truss strength comes from the truss design, and the depth of the truss, not so much the depth of the lumber from which the truss is made. My 24 foot span trusses are completely 2x4 material.
Wider spacing means whatever you put between the trusses has to span the wider spacing between trusses while holding the 120 PSF snow load. ONE approach to that is purlins between the trusses and the lower roof sheathing, so the purlins span the trusses and the sheathing only has to span the purlins.
In that environment if you are vaulting the ceiling I hope you've got a plan for venting the vaulted roof...