I'm surprised by those who think tube rolling wouldn't void the warranty.
I gather you don't have much technical experience with tubes. You can get a tube data manual and find that any given tube - say a 6922 for example - has to meet a set of specifications unique to that tube. See
http://www.mclink.it/com/audiomatica/tubes/6dj8.htm
for this particular example. It doesn't really matter which manufacturer makes the tube; if it is a 6922 it should meet those specs and be safe to use in any circuit designed to use that tube.
Any differences in sonic characteristics will be due to slight differences in physical construction - say one manufacturer's screen or plate may differ slightly even though the raw electrical specs are the same.
As noted before, any manufactured product can be or become defective. It is far more likely that the tube that caused your problem was simply defective (or headed that way) when you installed it.