1st thing
Rook is actually not an easy Demigod to play. He is very slow, so very vulnerable to 2on1s. You need to be able to judge when you need to bail from the lane, even if you are at full health. This is an experience thing so expect to die lots, suddenly and painfully.
Second I don't think Obscen's general build idea for Rook is listed in any guides, you should probably use it. It is the most powerful build as far as I am concerned. 
1) Tower I
2) Archer
3) Save
4) Tower II
5) Boulder Roll + Tower of Light
6) Slam I
7) Tower III
8) Trebuchet
9) Slam II
10) Tower IV
11) Boulder II
12) Slam III
13) Slam IV
14) Structual transfer I
15) Boulder III
16) God Strength
17) God Strength II
18) God Strength III
19) Poisoned Arrows
20) Stun Hammer
Overview of How to play
Rule 1: Tower your lane (you must be patient)
Rule 2: Never leave your tower farm when you are in lane, expand it slowly forward
Rule 3: Learn to boulder roll properly (even I fail at this 25% of the time, it is probably my weakest area with Rook) You really do look like a retard when someone at point blank range moves on an oblique angle so your boulder goes in the gutter off the map. 
Rule 4: Learn when you can and can't push a tower (there is also nothing wrong using your treb alone when you are level 8, safety over speed)
Rule 5: Do not miss any creep waves in your lane (this is probably my stongest area, I am usually 2 levels ahead of everyone at the end of the game, because I do my damnest to get full XP as rook) This makes a huge difference for this skill path build
Rule 6: Rook has very low armor, try not to take unnecesasary auto attacks
Rule 7: Structural transfer is a bad skill to take early (you have moreimporatant things to take), but near the end when your build is finished it can be a good way to hold a portal inbetween fights.
Some notes
Some people swear you should only take up to tower II, don't listen. Tower III and IV might take awhile to build up, but it is a real pain in the ass to take down, even if they kick you out of lane they are still going to get hurt removing it. When you are level 14ish, you can usually survive a 2on1 with all your towers in play.
Godstrength is a deceptively bad skill to take early. Rook's auto attack is very slow so 50 damage is not that big a deal. At level 8 you get cleave for free anyways, so you can clear out creep waves just as easily. However, at the higer levels, Rook's auto arttack speed starts to get a little crazy, and 150 extra adds up to insane levels of DPS so it becomes a bad skill to miss out on.
Skills 19/20 are optional choices, but I like poisoned arrow and stun hammer, because, if you fight me, one of us is not leaving alive.
Items
(start) Blood of the Fallen + Scaled helm: Maintaining 2 towers early is safer then more life.
Then stack life/armor and mana as you can
Unbreakable
Banded
Scalemail
Vlemish
Sell Scalemail, get Nimoth
Sell Scaled and get Plenor
Now, watch every replay of your games.
Find places when you weren't patient and took damage that could have been avoided
Find places when you didn't leave a lane and should have because you were in danger of being killed (you should rarely be in a heart stopping situation as rook where yuu say "OMG I don't believe I lived". You are playing right when you don't get in these situations)
Find places when you died, learn not to do that.