we also went from a popup to a Roo 23SS.
first, get a set of tandem wheel chocks or make you own, like i did. plastic wedge chocks won't do the job.
simply use Lynx Levelers or wood under both wheels on the side that needs to be raised. you do side-to-side first. .
once you've got side-to-side done, then chock both sides of the trailer with your tandem wheel chocks and disconnect the trailer from the tow vehicle.
then use the tongue jack to do front-to-back. having an electric jack makes the job so much easier.
once you're level, THEN put the stabilizers down and be sure not to overtighten them or you'll bend the frame. remember they are NOT levelers.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC