Step 1. Be in base with homeguard
Step 2. Press Q
Step 3. Teleport near destination
Step 4. Press 1 and 2
Step 5. Press D
Step 6. 9999 MS
Step 7. ?????
Step 8. Profit

But in all seriousness, you probably noticed by now that this build has Yommu's and Talisman of ascension, so you can already see where I'm going with this.
Rammus roll is one of the only % speed buffs in the game that apply on top of other speed buffs. This means that if (for example purposes) you have 300 base speed, and a 50% speed buff, as well as Q, which accelerates to up to 165% bonus speed (but its only like this for a split second. the average speed is 70% during the middle of the roll), normally it would be like ( 300 + 150 (50% of 300) + 495 (165% of 300) ) = 945 MS, BUT with Rammus Q's unique ability to stack with other buffs it's ( 300 + 150 (50% of 300) + 742 (165% of 450 (Base MS + other buff) = 1192 MS, so with higher Base speed ( Rammus has a base speed of 335 and boots (+60 flat MS), he can reach some ludicrous speeds. Add Ghost and Yommu's on top, the Homerunner passive from Zz'rot portal (30% MS buff) plus Homeguard's 200% MS buff to boot, and you can reach speeds that will make your enemies say.

Want a more serious guide, that's actually indepth and extensive, explaining the strategies, mechanics, and comboes behind the champion?
My Yasuo guide: http://www.mobafire.com/league-of-legends/build/yasuo-mid-s5-match-ups-for-most-mid-laners-lt-5-1-gt-409188

REMEMBER: This (This one, not the one linked above) is a somewhat trolly build, you WILL get flamed and you WILL get reported by tryhards who don't realize the game is about having fun. But, for the love of god, please don't use this in ranked, it's a completely different, more competitive, environment. Please respect others, use this ONLY in Normals.