Bodies typically progress outward rather than inward. (See Why is the Moon receding from the Earth due to tides? Is this typical for other moons? .) The only orbiting bodies that might approach are ones that orbit faster than the main object spins, IOW, closer than synchronous orbit. Even then they could recede if locked into resonance w/ other bodies, eg, moons, further out. (See Does anyone know why three of Jupiter's largest moons orbit in 1:2:4 resonance? .) Deimos and Phobos are approaching Mars though.
Supposing you do have an approaching body, eccentricity and inclination will be damped into a slowly degenerating circular orbit. As the body approaches, the acceleration of the body, through the main body's two tides' net pull, increases roughly as the 6th power of distance. (See Tidal Evolution of a Planet and its Moon.) And tidal heating will soften the body, allowing even more deformation.
It is a runaway process at some point, and that point may be quite far into the Roche limit. How far would depend on body size, material tensile strength, structure of the body, thermal conductivity, changes with temperature, etc. It would take detailed modelling to describe the process. The catastrophe could start in the most vulnerable locality of the body and spread from there (Ka-Boom!), or involve the whole body concurrently (Squish!). It may not go "boom", but at the end you might be able to observe it in real time.
Another possibility is that the body will start disintegrating at the near end, where the forces are strongest. By conservation of momentum (or would it be energy?), every time a piece leaves, the rest of the body is pushed slightly the other way, sending the remainder slightly higher, delaying the process. This could take quite a while, but there is always a chance that things will destabilize at some point and go into catastrophe.
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