While mining a roid, and being very close to it, it can be quite difficult to re-select it (to check its temp for example) once other objects (ships, bots, other roids) have been selected. It would be nice to have a key to press and select it.
(Now maybe this belongs to the Bugs forum: it is difficult to select a big roid, 20m in front of you, filling up your whole screen)

Did you try facing it and pressing 'b' for select front? Unless the roid is enormous, you shouldn't have an difficulty reselecting it.

Or you might try Select Previous which is by default set to '['

Death Fluffy, 'b' key is not helping, and yes, usually, the roid is enormous :-)
Select Previous doesn't help either, as the roid I'm mining isn't necessarily the "previous one" in the roid list...

A post on a similar subject in Bugs forum: http://www.vendetta-online.com/x/msgboard/2/22867

Then in the mean time, perhaps using TargetLess vs 1.7.7 would help. You can store your favorite roids and scroll through list of favorited roids within range. IIRC you can even name them.