Bulbophyllum: how to recognize dead roots?

[tropterrarium]

I have a Chirrhopetalum sikkimense/Bulbophyllum roxburghii (Seller and Amer Orchid Society folks disagree on ID) for three years, that is growing well and flowering well, too. The plant is a pile of bulbs and leaves in a small pot, with roots covering everything like a spider web. I remove the spent stems of the inflorescences, but wonder whether the brown roots are dead and can be safely removed. The roots start out white with green tips (live for sure), then turn beige (hmmm?), then darker brown with the skin on the roots separating from the core (dead for sure).

So, how do you distinguish dead roots from those that are just a bit older but still perfectly functional? The question is particularly in the beige to brown transition area.