I have a Shamrock 19 2011 - twin of the Roo.
Unless they have changed the model, you have a Suburban.
Make sure you have water, either in the fresh water tank or city water connection, open the taps get cold and hot water running. You may have air in the pipes, but it will eventually settle and a steady flow will come out.
I always light the burners on the stove for a minute or so, to get rid of any air bubbles in the propane lines.
For propane: simply flip the inside switch, it will light up for a few seconds and turn off. Listen carefully you will hear the burner working. That's it, you will have hot water shortly (20-30 minutes I think)
For electric: you have to go outside, remove the cotter pin and flip the lever to get the heater to work off electric instead of propane, you can also use both electric and propane for a quicker delivery.
Denis & Diane
2010 Sabre 31REDS
Ford F-250 2011
* Happy Campers *