Hmm - if it'll function without a round in the chamber it sounds like it's not fully going into battery? The ross bolt should try to close itself when the trigger is pulled (and the bolt's properly assembled)... since you've tried two bolts and it has done it on both of them, it's not the bolts.
When a round (or piece of brass) is chambered and the bolt cocked, then you pull the trigger, is there any movement whatsoever? I'm wondering if the gun isn't able to get into battery so the whole assembly just locks in place, since the spring action will try to close the action, but if it's as far forward as it'll go with whatever's stopping it, it'll just stay where it is.
I guess without having someone look at it:
1) Does the sear move without a bolt in the gun? IE can you see it drop down in front of the roller when the trigger is pulled?
2) With the bolt in the gun but no round chambered, does the trigger and bolt work correctly, IE dry fire?
3) If it works correctly, does the bolt body move forward at all? IE is there a way to index a point on the bolt body and measure off the receiver ring so you can tell if it travels forward at all after the trigger is pulled?
4) can you place a sized but unprimed piece of brass in the chamber and repeat the process and dry fire?
5) If yes, can you place a primed piece of brass in the chamber and repeat? does the primer fire, is there any marking on the primer?
If you get to point 5 I'm stumped.
Points may have a..... point (badum-tss) on something fouling up the lugs inside the receiver ring. If you've got a curved dental pick and a good light maybe do some passes and see if there's any built up gunk hiding deep down in a crack that's catching a lug? Also see if the light shows any burrs or cracked/warped surfaces or anything like that in there - either on the bearing surfaces or the breech face that might keep it from going into battery properly.