The Good Game Team Comp
Okay, so I'm not gonna put in builds for each champ, just look up the top builds for them, but I will say this, you cannot go wrong with this team comp.
You might think that ashe is the weak point, being she is primarily a 5v5 champ but if she is played well she is key. She puts out good damage, he slow is vital, and her ult is devastating to teams. She is quite item based so make sure to play aggressive to start and try to get some early kills. The only downside is how squishy she is, but that's where rammus comes in.
With his taunts, his slow and aoe ult, he is pretty much a good game kinda champ. If any of their team tries to focus ashe you have the ability to taunt them off and by the time your taunt is finished, most likely they are gonna be dead. You have some good damage and tanking towers is easy with your defensive ball curl and ult. Plus his powerball will let you get pretty much anywhere on the map within seconds making him the ultimate ganker / saver.
Not to much to say about jax. Everyone knows he is OP and will literally rip teams apart if he even gets slightly fed so I hope there is no arguments to him being in here. He has crazy nuke damage with his leap and empower and with rammus keeping the damage off, him and ashe will rip teams to shreds. Again the only downside is lack of cc since they nerfed his dodge item (phantom dancer) but rammus has more than enough taunt to go around.
Me and my buds have gone pretty much undefeated playing these champions, and the key is to play very aggresive off the start. Rammus can take the hits while ashe kites until one of them gets to close. A simple flash, taunt combo is useually good enough to kill most squishy - medium health champs early game (plus ignite is a nice little bonus).
Try it out, comment with some ideas and give it a rating, thanks.
Some key items
I don't have time to go through the builds for all the champs but I will mention a few key items for this team.
As usual, rammus once he gets sunfire is pretty much golden. The armor and health lets him taunt and take the hits while boosting the damage he puts out. Also, its relatively cheap so with a few early kills you should have it in no time.
Although she already has the slow, a frozen mallet is a great idea. Ashe being the squishy champ she is can always use some health and with her super slow you can kite and harass with ease. No way can champions run after she has this item, her slow gives time for rammus to get in there and wreck kids with his taunt. Then its Jax and boom, ace!
Jax has a pretty regular build. Guinsoos rage blade is a great item as it stacks with his ults passive to make him incredibly strong as fights progress. I tend to like jax slightly more ap based as ashe already deals good ad damage and it makes his leap strike and empower way to good.