Technique is quite important on the erg (rowing machine) but most new rowers/ergers screw it up. Make sure you watch some youtube videos and get the form down -- it's legs-back-arms, arms-back-legs in a nice continuous motion.
What kind of pace (split per 500m) are you holding during your 2000m pieces at moderate effort? And what is your primary running event?
The main rowing distance is 2000m, so rowers tend to do a lot of long, constant steady state and short intense workouts for anaerobic sharpening. These workouts can be pretty taxing on the body because rowing is much more of a power sport than running, so I'm not sure I would recommend them if you're focusing on running. However, if you want some short workouts, try:
8x500 w/ 2 min rest @ 2k race pace or faster
3x1500 w/ 4 min rest
A longer workout I like:
10 minutes broken down into 4'-3'-2'-1' at increasing strokes per minute, usually 18-20-22-24 or 20-22-24-26. 2 or 3 reps w/ roughly even rest. Should be near max power at the low ratings
Other than that, just lots of steady state (10k-20k), which you can break into smaller chunks. Also 5ks at constant but increased effort are good.