Light Frigates, what roles do they fill?

Mostly to hamper the ability-dependent support cruisers. The Cobalt's Sabotage Reactor disables abilities briefly and attempts to use that ability during that time cause damage, the Skirmisher's Interference doubles cooldown time and antimatter cost of abilities and the Disciple outright steals the antimatter of enemy ships.

These guys are also effective against carriers and flak frigates.

I don'y build light frigates late game, becuase a Kodiak, a Destra, or a Enforcer would destroy them in a few shots, so unless you plan on building a lot of them, which is not a cost effective way to kill capital ships or LRFs, they're useless. Just stick with LRFs, HCs, and Capital Ships with Carriers and Support ships late game.

I am only a newbie, but i often find, start, mid-game and end-game, at least for the way i play, that having 10 or so diciples is a good way to deny anti-matter to the opponents, and to keep my own fleet well charged. Of course my perceptions could be wrong.  Anyway, having them at any stage for me, seems to help. I play a lot with mods loaded, so perhaps what i am describing is an effect of the mod, and not the diciple. You could try it and see if it makes any significant difference. If your play style is consitent, then you should notice.

Just my opinion,

=Teal

They are obsoleted by people spamming missile frigates, but that in turns get obsoleted by carrier cruisers. As fleet composition becomes more balanced and support cruisers start showing up, light frigates come back into their own because they are cheap, do good damage and severely impair the function of support cruisers.

i mean, if the opponent brings a lot of Overseers or Subjagators to a fight, that can really change the whole dynamic and Light Frigates are the best counters.

A light frigate is also about as tough against bombers as a heavy cruiser is, and for far cheaper. 

The other advantage of light frigates is that their weapon research appears low on the tree while heavy cruisers tend to use more advanced weaponry.

Finally, in a siege situation they are against reasonably resistant to strike craft while building much faster than heavies.

hmm lets see now roles for light frigates..........oh yeah i know.. CANNON FODDER!!!!!!

Light Frigates are still quite cost effective when massed. Especially if you need to split your army up.

Tactically speaking, it's far more annoying to focus fire on a bunch of small ships that keep retreating (due to user micromanaging) than a few big, slow ones. Thus, cobalts can actually be as hard to take down as kodiaks, for less cost. In a team game, cobalts benefit from the Halcyon's Amplify Energy Aura, whereas the kodiaks have no relavent aura.

Destras are probably a better choice than disciples however, due to their area of effect attack, and the overall weakness of disciples.

Vasari light frigates are beasts when upgraded. They can repair while being focused on and hold on much longer than cobalts or disciples. Enforcers can too, but having them sit around means sacrificing a larger comparitive portion of your army.

The number of light frigates deployed are a good measurement of anti-skill.

Fear the mighty Cobalts-only fleets!

Bingo.

Early game they are all you can build

mid game they tend to get blown up

late game they are a necessity to balance out the support ships and carriers

Aye, especially as of 1.1. With the increase in importance of carriers, light frigates are even more important opnce you have their higher level abilities researched.

I keep trying to tell people I have been using them successfully against carriers in the beta.  Now they will learn. 

The one caveat is you have to keep them away from any LRM's and HC's the opponent might have.  If the opponent has a lot, then you probably shouldn't use them.