Hi, welcome to my guide on Rammus. Rammus is a great tank that can absorb the blows made by the enemy team. With not much HP but a **** load of armour Rammus is very hard to take down. I will be taking you through 3 builds which are:
1. Normal Laning Rammus.
2. Jungling Rammus.
3. AP Rammus.

Pros=
Great Armour
Deals alot of damage
Hard to ignore because of taunt
Great ulti which will help massively in team fights
Very fast at travelling across the map
Great farmer
Great pusher
Amazing chaser

Cons=
Not much HP at the start which makes him somewhat vulnerable
No ranged attacks

The runes i take for Laning Rammus are: HP Marks, Armour Seals, Magic Resist per LVL Glyphs and HP Quints.

Jungling Rammus: Magic Pen Marks, Armour Seals, Magic Resist per lvl Glyphs and HP Quints.

AP Rammus: Magic Pen Marks, Armour Seals, Magic Resist per lvl Glyphs and AP Quints.

1. I start with a Doran's Shield and 1 HP pot . When you can return to base and get your Ninja Tabi . (Please note that if there are a few heavy casters or stuns go with Mercury treads immediately). Once you have enough for 1 or more of the items in Sunfire Cape go back and build it up. Getting Sunfire Cape early will help loads with farming up some more gold from minions. After Sunfire go with Banshee's for the health and magic resis.
after Banshee's if the other team are more magic damage go with Force of Nature but if they are physical go with Thornmail . If there is no magic damage instead of Force of Nature go with Randuin's Omen . As your last item grab gaurdian angel so you can stay longer in the team fights. During the laning phases of the match grab a hp pot whenever you can. Getting blue buff will let you be able to spam your abilities especially you ulty with a 25 second CD at ulty lvl 3 it is great for Team fights.

2. Jungling with Rammus is fairly easy by starting at Double Golems, moving onto Wraith camp, then Wolf Camp and finally Mana Buff. Head back to base and heal then gank or get Red buff. You can also start at Mana Buff soloing it or if your not sure if you will kill it get a mate from top to give you a hand.

Items- I start with cloth armour and 5 Hp pots. I try to get a Giants Belt right away instead of the armour for Sunfire. As i said before sunfire is very important for farming. Always try and gank early. Getting the early cash will benefit your team greatly. It is a lot easier to gank when you have your Ult handy. Ping the champ you want to target before initiating with roll before taunting, popping your defence curl and ulting that should be enough for the kill along with your teammates damage.

The items are the same as build 1.

Start with Doran's Shield and HP pot. Get the Giants Belt for the HP followed by Tear of the Goddess . Get Sorcerers Shoes for the Magic Pen. Finish up Sunfire Cape and then Archangels Staff . Banshee's Veil and then Abyssal Scepter and finish it with Guardian Angel . The play style is the same as The Laning Build. Rammus's Ult will be a lot more powerful because of the AP. But just be careful as you are not that tanky with these items. I would recommend this build for 3s or if you are versing a terrible team in 5s.

Use your rolling ball to initiate. Remember you have to control the rolling ball you can't just click the champion and expect Rammus to weave through all the minions.
Remember to taunt the squishys so your team can put them down. right after your taunt put on Defence Curl as when getting hit with it on a fraction of magic damage is put onto the attacker. Then pop your Ultimate.

Build 1- I take the 0.21.9
Defense= Dodge along with the speed boost, Block physical attacks, 4 points in HP, 2 in Ability Power and 1 in the Bottom one.
Utility= Ghost boost, Mana regen and EXP.

Build 2- 0.16.14
Defense= Similar to build 1, Armour and Magic Resist along with mana regen, take less damage from minions and HP.
Utility= Mana Regen, EXP Buff duration and flash boost.

Build 3- 9.21.0
Offense= Ability power, Cooldown reduct and Magic Pen.
Defense= HP regen, block physical attacks, HP, Ability power and Decrease

I take flash and ghost when laning with Rammus. Flash because it has saved my *** countless times from ganks or ulties like Nunu's and also initiating team fights. Ghost because it is a good for chasing down enemys and running away from them.

When Jungling i take Smite and Flash. Smite is great for the faster jungling and flash like i said above.
And AP Rammus is the same as Laning Rammus.

Please remember that your ulty can take down towers and with such a small CD don't be afraid to use it.
Hope you like this build it works great for me and please comment with either Positive or Negative feedback. Please don't down vote without leaving a comment. Have fun playing Rammus!!