Can I partially suspend an angled climbing wall from my garage trusses?
You need to define the type of garage ceiling you're looking to use. Not all trusses can be used for downward forces (say it keeps the walls from spreading) and if you're accidentally mis-describing them you could be getting some bad advice.

That said, assuming your climbing wall touches the ground the load will be carried there. Lateral forces on the side of the wall from 'pulling out' are supported by the cross bracing in ceiling. I'll see if I can find the article on design I read on the 'net about 3 years ago.

Edit: OK, going to give my non-civil-engineering view on this.
https://www.menards.com/main/buying-guides/building-materials-buying-guides/roof-truss-buying-guide/c-19431.htm

The example image shows all of the load being pulled downwards (compression) to the floor, and the ones nearest the wall providing tension to pull the rest towards the wall. You should have a large piece of anchored plywood or 2x8 back there to bolt into- lag bolting into your 2x4 sticks in the garage. Then you can attach multiple points to the 2x8 and the 2x8 can resist twisting the rear wall. 

The bottom chord of your attic is in tension- it's to hold the walls from spreading. The upper chords are in compression and are carrying the load to the double sill plate around the base. The remainder of the web is stiffeners and compression/tension. Diagonal'ed boards in the attic prevent your roof from twisting around.

Just really limit how much 'weight' the ceiling is holding. If you do the example you've got, really emphasizing connecting it to the wall, it should be fine. Assuming of course the wall is connected to the floor somehow...