Yo, Rammus/Lulu main here. Here are some tips to survive as an AD vs. me.
1. Last Whisper and Bloodthirster. Get them, otherwise you'll end up killing yourself on his W and thornmail, while dealing no damage vs several hundred points of armor. Also, the damage reflection from both is all magic, so plan accordingly.
2. Avoid getting in melee range for any reason while you are near one of their turrets, especially as a melee character. You will be taunted and take several turret shots (for extra damage due to the taunt's armor reduction) unless you can cleanse/QSS it away.
3. Unless you know exactly where Rammus is, avoid backcapping unless you have backup.
4. Speaking of which, buddy system. Find your mage and stick to them. At level 18, a Rammus generally has 120-150 MR as long as his W is down, and don't usually stack a lot of health, so they'll do a decent bit of damage, especially with a Void Staff.
5. Down bother focusing him if his W is up. Just don't. Especially if the Rammus has a Rylai's for some reason (I've seen it before). Then you'll just end up kiting yourself.
6. Don't just stand there while his ult is up. Those quakes add up quickly.
Listen to this advice and I'm sure I will find you very annoying to deal with.