I believe that the hate comes from misunderstandings (as usual).
Firstly, roamers come to PvP unconsciously thinking that their solo skills are enough to help the team win. In fact, these skills do matter, but are not enough, as has been said by other posters – rotations, map awareness, node control are essential aspects to master as well. Being a former roamer myself, this is something I had to learn the hard way (and am still learning).
Note that any player proficient in one game mode thinks he’ll do reasonably well in other ones, even though there’s no basis for this. A WvW roamer might not be able to solo the Lupicus in under 6 minutes. A PvPer might not solo-take down a whole camp in 40 seconds.
Secondly, PvPers who have never done any roaming don’t really know what it’s about, and put in the the same bag than zerging (for those who do not know what solo-roaming is: you take enemy camps and protect your own, annihilate enemy roamers, protect or attack supply routes, contest enemy holdings, scout enemy movements, all of this coordinated with the strategies of the map commanders). It’s simply the standard whole community group hate coming from ignorance – and of course, every community is subject to this.
PVEers are not differentiated between Open World content, EotM, HL group dungeon, solo/duo dungeon. WvWers and not differentiated between zerging, solo/group roaming, optimized guild runs and GvG. PVPers are not differentiated between Conquest and… err… still looking (although we have some gw2 gold eu in some players’ initiatives, like 2v2s or 3v3s). Nevertheless, all these game sub-modes require different skills, some being pretty high level.
Just ignore the hate (might not be easy!), and keep an humble mind when playing. Just my 2c.