If you picked up Mines of Moria, then you'll hae the rulebook with it.
As for a start up Rohan army. I guess Rohan is not really good for starters as their tactics are somehow tricky and mistakes unforgiving. but anyway, better start up with all foot warriors for a quick game or two then when basic rules are clear you can replace few warriors with a hero. A minor hero (rohan captain) would be nice for a start, though Rohan is blessed with low cost Heroes like Eowyn too so you can have a choice. later on you can add couple of Riders, or may be add in the riders then the Hero later if you feel it could be more fun.
a starting army could be (Eowyn can replace 2 warriors with B+ 3 warrior with TS):
7x Warriors of Rohan (Sh)
8x Warriors of Rohan (TS)
5x Warriors of Rohan (B)
148pts
you can then replcae all TS with 3 Riders equipped with bows and TS, and add TS to all Warriors with Shields to be (Eowyn can replace 3 warriors with B+ 1 Warrior with Sh+TS):
7x Warriors of Rohan (Sh+TS)
3x Riders of Rohan (TS)
5x Warriors of Rohan (B)
148pts
also you can replace 1 rider, 2 warrior (Sh+TS), 2 Warriors (b) with Mounted Eowyn.
with time you need to stress on hit and run cavalry tactics which will require using Heroic actions.
couple of useful articles:
http://www.one-ring.co.uk/phpBB2/kb.php ... icle&k=194
http://www.one-ring.co.uk/phpBB2/kb.php ... icle&k=569