The last 1000pt Rohan List I played was this:
Epic Heroes:
Theoden
Eomer
Erkenbrand
Deorwine
Legendaries:
6 Companies King's Guard Mtd
Plus Royal Standard of Rohan
Common:
6 Companies Royal Knights
Theoden's Guard Battlehost
Now for Wrath, Now for Ruin Fortune
I deploy Theoden in the King's Guard while I deploy Eomer, Erkenbrand and Deorwine with the Knights. With Erkenbrand and Theoden both calling Epic Charges, this army hits the enemy line hard. To counter Dragons, Balrogs, Khamul and the like, Deorwine and Theoden can use Epic Sacrifice (a desperate measure I know) to reduce the number of wounds their formation suffers and perhaps win the fight. The follow up charge from For the King guarantees the utter devastation of the enemy formation.
You could also build the following army;
Epics:
Erkenbrand
Common:
Riders of Rohan (4 Companies w/ Capt)
Riders of Rohan (4 Companies w/ Capt)
Riders of Rohan (4 Companies w/ Capt)
Riders of Rohan (4 Companies w/ Capt)
Riders of Rohan (4 Companies w/ Capt)
Riders of the Westfold Battlehost
With the Valour of the Hammerhand Virtue, this army won't suffer too badly against enemy monsters or cavalry. Able to harass the enemy with bows and mobility, the Riders could stay out of combat long enough to whittle the enemy ranks down before sweeping them aside with a cavalry charge.
Yes, both lists are weak against armies hiding in defensive terrain but unless you take a large Royal Guard contingent Rohan always struggles to take defensive terrain.