It's ok if you're a passive roamer who just watches the flank i.e. GeaR. Haven't seen shadowburn do anything this season that's legitimized his decision to run black box and conch - he'd be much more effective just running default and using his good DM to hit 4 good rockets.
For most players (and teams who rely on their roamers to make space, force ubers and distract) RL/gunboats/equalizer is gonna be the best loadout.
Paintrain if you want to make distracting with backcaps etc a big part of your team plan (limited effectiveness once teams figure out you're doing this but still pretty good), black box if you want to just hold the flank and have two DM-heavy scouts who can rip through teams with an aggressive pocket, shotgun if you're passive like above but have really good hitscan aim and can 1v1 scouts consistently, and conch if you're retarded (honestly cannot see any reason why you would run this on roamer, it makes no sense if you're playing against reasonable-level teams because you have to play so passively or you die before you can make use of it, plus you have to be with the combo on pushes which fucks stuff up so badly).
That's my opinion on it anyway. You don't see many loadout changes in EU prem at least for roamer because the "default" (i.e. gunboats eq) makes the roamer very effective at helping the team - the other unlocks may help you in certain situations but overall I think you're gonna let your team down in crucial scenarios where they need you.
EDIT: I think I made shotgun seem more viable than it really is - you legitimately need ridiculous shotgun aim and you need your team to only need you to hold flank. Same as black box, you need to be only holding the flank and taking those scout fights, you won't be able to jump anywhere or make room or distractions, even forcing will be a pain (but you will get at least one drop to shotgun :D)