My best experience at Roskilde ever, took place one friday night back in 1992.
First, Pearl Jam did a great gig.
Then, Denmark beat Germany 2-0 in the european football championship final
(note to USLANDER aka Patrick; Yeah, I said football, "when in Rome" lol)
Finally at 23:00 NIRVANA entered the stage, delivering what would turn out to be an EPIC concert. The grunge genre had just hit Europe, Nirvana was at their peak at this point,
and keep in mind that this was back when stagediving was the rule, not the exception.
I still get the shakes just thinking about it.
http://www.youtube.com/watch?v=s8zTEYk0TmY(Nirvana interview at Roskilde)
http://www.youtube.com/watch?v=gaE8mbAX3_U&feature=related(In Bloom, Breed, About A Girl)
http://www.youtube.com/watch?v=venOidRgDHg&feature=related(Something In The Way, Encore/Break, Come As You Are)
http://www.youtube.com/watch?v=4ljUJBAsDqg(Territorial Pissings)
Other worthy contestants would be:
JIMMY PAGE/ROBERT PLANT 1995
RADIOHEAD 1997
THE PRODIGY 1997