against 2 dps, 2 mage and one tank?

Unless you have a specific question, please refer to the guides posted in the sticky on this forum, or visit a site like solomid.net. These guides will tell you what to do against a balanced team, as well as against unbalanced teams (when to buy thornmail, when to get an early Banshee's, etc).

FON
Sunfire
Aegis
merc
banshee
GA

Check out this Rammus Guide

You'd want something like:

Mercury Treads
Aegis (unless you have a support building one)
Sunfire Cape
Banshee's Veil
Frozen Heart
Force of Nature

Other possibilities are:
Guardian Angel
Randuin's Omen

I wouldnt get caught up on a "final build" most games you dont reach it. Focus on building the resistances that the game calls for at the present time, they might be a balanced team with both the AP champions completely fed, making magic resistance much more important then armor.

I usually play Ram with:
-Thornmail
-Abyssal
-Sorc Boots
-Sunfire
-UP TO MATCH (usually Zonya)
-UP TO MATCH (Usually FoN, QS Shash or DeathFire Grasp)

I have Spell Pen runes and Gold Quints, as I play Sona.

With that build, each attack on yourself, and near you, is boosted by a lot, and you still can do a good tank job.

As spells I get heal and smite (usually jungling) or heal and fortify (splash)

- Mercury treads
- Force of Nature
- Sunfire
- Banshees Veil
- Warmogs
- Guardian Angel

I know I know "WARMOGS IS NOOB ITEM" but there comes apoint where defence becomes hard to increase the damage that it actually reduces and health becomes a better investement and his ulti can let him farm well dur to it being AOE and on a relatively short Cooldown

You may also consider fitting in an ageis earlier if no-one on you team has one and not getting the Guardian Angel

Rune Page
9x Flat armour Yellow
9x Magic Resist per level Blue
9x Armour Pen Red
3x Flat Health Quintess

I use this runepage to jungle as well

You have all the right items listed in this thread. The trick to playing a tank is getting them in the order needed for that game. Check the scoreboard when you're about to buy. Do they have a fed member of the team you need to counter? Who's rocking some good damage items? Buy what counters those guys even if it means forgoing finished items for a bit and just stacking chain vests and negatrons for furture upgrade.

Also pay attention to your death recaps. Sometimes that scary AD carry won't even attack you until last so buying defense against them is less of a priority but Annie always tries to burst you down you as soon as you initiate.