Hello, this is my dominion build for Rammus.
I´ve used this build everytime I´ve played Rammus on dominion, and never lost.
I know that they are still working on dominion, and that everybody is new to it, so it´s hard to decide wich item to use.
But as I said this has worked for me.
Rammus is a really good champ for domion, because he´s fast and can take a lot of damage wich is good when capturing the points.
Remeber, as Rammus don´t play defensive, you want to be where the action is, and you waqnt to be the center of it.
Rammus is not a mana dependet tank, nor has he problem with his base cooldown.
You just need to know when to place what spell, wich is simple.
Rammus is one of the easiet tanks in the game, but one of the most rewarding.
The way to do damage with Rammus is to take damage, you want the enemy to hit you, to focus you. So try this out and let me know what you think.
(sorry for the spelling errors)

So good luck, and hail Rammus

Ok, first of all, ghost is a must in this game mode.
Makes you move fast to where you want.
No questions asked? Good.
And now to my choice Garrison, makes it easier for you and your allies to cap a point.
(Garrison on enemy tower makes the tower do less damage)
And to defende a point.
Use it as often as possible.

Start with a chain west, boots of speed, and 3 health potions.
Make sure you always have potions.
Then rush a Thornmail, followed up by boots of mobility, this makes you fast and you can take a lot of damage, and give a decent amout of damage back :D
Then, I buy a negatron cloak for some magic resist, good to have.
Then a sunfire cape, to do more damage when you tank, and some health.
If you don´t have troubles with magic, then buy sunfire before the negatron.
Then I go for a Abyssal Scepter, for some damage on "q" and "r".
After that you have to decide what you need, Warmog is always nice to have, can stay out on the field longer, and take more damage.
On the other hand some abilty power is always good, and think about the slow effect, perfect for your "r" when your "e" is up.
It´s all up to you.