WvW roaming
It’s hard to say. For solo roaming, it’s very hard to beat the amazing pressure + survivability of a rabid/dire mix. For groups larger than three, zerker may be better since you’ll trade your survivability and sustained damage for lockdown and burst, which could be better if you have a good group.
I roam a lot in a HgH build and I use dire armour and weapons and rabid trinkets, this I find to be really effective! I run boon duration runes and food and tuning crystal for condition damage, I get 80% boon duration but only 20% condition duration! however with full stacks from sigil of corruption and around 20+ stacks of might I still have around 2k+ condition damage which is more than enough. I use to run a 3 kit build but lacked condition removal, this build I find a lot more robust with plenty of oh Kitten escapes if you run upon a Zerg etc.
http://www.twitch.tv/kryank
http://www.youtube.com/user/minikryank
berserker is generaly very bad for roaming, unless you have alot of disengages.
roaming usually gets you into to outnumbered fights and you if you can’t stand the pressure of being attacked by 2-3 guys, your extra damage won’t help.
engie roaming vids: http://www.youtube.com/channel/UC9NnXVfY4vRU1F-X7b1Oorw/videos