This is a basical Rammus tank build.
Your Summoner Spells are your own choice.
I just prefer fortify as a tank because it can be very useful and clarity is usefull,too because u get mana problems quite often.
Level 1 Ball is great for grabbing FB assist and after that level defensive ball and taunt as fast you can. i think that taunt is most important so i try to maximise this ASAP.
Start with a Ruby. You might have no pots but a lot of health and allready one part of Aegis. After you got your boots the next item is dependent to your enemys team. if they have lots of strong and anoying caster i would prefer banshee's otherwise you get Aegis.
Than you have to grab your core item: Thornmail.
When you got this most of the dps carries cant kill you without dieing.
After grab your first sunfire. it has everything you need and a nice plus with an additonal AOE.
Then Grab your Guardian Angel to become absolutly unkillable.
The last item is again enemy dependent: Many Casters? Grab Force of Nature and make them as useless as the dps/carries. No damgerous casters? Grab a second sunfire and BURN THEM DOWN!!!!!
How to play:
Well its easy. Early on you should get a melee dps on your lane with a charge or jump(for example yi/xin). wait in the brush, ball onto an enemy, taunt, your allied jump him,gg.
Later on you can gank very well.. Just again wait in a bush, mark, ball in, your allies kill him.
Endgame you have to initialize so ball in, deff ball on, taunt the most anoying carry, ulti on and pray that your allies help and rip their faces. When you have finished this build you have around 400 armor without def ball. I had a gankplank against me, and he did 300 damage to himself with parley, while i got something between 10 and 50 damage, so melees just cut themselves into pieces if they attack you.
Rammus is team dependent. You need some dps in your team, but against melee nukers you are the most op tank ingame.
Try this build, comment and GET THEM ALL!!!!