First off: Welcome to the waaaaaaaagh!
Second: That is a very wise move putting rams on your trukks. Cover is your friend. Immobilized trukks are the bane of your existence.
Third: Rokkit launchas will very rarely hit, but can make your opponent freak over the
ap 3 aspect. I have played matches where I made an opponent jink his jetbikes because he feared the
ap 3, and as a result, he could not hit much of anything next turn. Rokkits are good for fear, big shootas are good for usefulness. It all depends on how you want to play it, and how your oppents play when faced with rokkits.
Fourth: Pain boys are good, but they really shine in giant 30 boy mobs. You gain a lot more survivability. 30 boy 'eavy armor mob with a painboy in the back is expensive, but you will be hard pressed to find a more survivable blob.
Fith: Dude, get lootas. You can NEVER have too many lootas. 15 man squads are very capable of ripping infantry and any
AV 13 or lower tank apart. There are only two issues with them. 1: If they are on foot, it can be hard for every single one to see the target without having line of sight blocked by terrain or a trukk. 2: they are very squishy, and most people make them priority target #1 (and for good reason). You have to give them something to make them survivable, or just bring so many that your opponent can't kill them fast enough. Personally, I put them in a battlewagon, but that is not the only way to go. Just play around and see what works best, or is just the most fun
Sixth: Bosspoles. Get bosspoles. They only cost 5 points, but they make your boyz a lot less likely to turn and run when the unit gets under 10 boyz. Trust me, your boyz will stay stuck in the fight a lot longer.
Seventh: 'Eavy armor. When I started orks, my reaction was "4 more points for a guy in armor? That's almost an entire boy! I'd rather get more boyz!" While that was a very orky reaction, when I eventually did try out 'eavy armor, I noticed that my survivabilty went a lot higher. Let's face it, boyz only have an initiative of 2. Unless you are playing against necrons, you will always go last. Having a 4+ save instead of a 6+ save makes all the difference, especially when it comes to trukk orks, seeing as you can only have 12. In the end, survivable orks = more attacks. And more attacks = good! So I suggest giving your trukk boyz 'eavy armor. Now for large blobs? That's more up to you. But I always have my boyz in armor.