I recently removed a tongue and groove ceiling in our old timber frame barn ~1900 that was attached to ceiling joists (long 2x4's) nailed to every other rafter. Then, assuming they were not structural, removed about 2/3rds of the joists to open up the space before it occurred to me that they could be. A friend told me they likely were not given the beefy timber frame construction and the fact that the rafters join the big beams and are likely supported by them but he suggested I check here just to be sure. unfortunately I can't seem to attach images-- maybe because I'm a noob? Anyway, based on my description is there a chance the roof could sag or spread? I'm thinking the joists were nailed there just there to attach a ceiling but want to be safe.

Thanks for your help!