matching amplifer output phase to subwoofer phase

I have a PHASE INVERTING amp by (jeff rowland), the subwoofer I am using (paradigm seimic 12) has a phase adjustment knob, is it logical to invert the phase knob 180 degrees from O to match subwoofer phase to amp speaker output?
IME, the phase (or better, if available, polarity) of the subwoofer should be set to minimize bass cancellation due to reflected energy. One polarity setting will usually provide a much better result than the other. I gather that this result is a fairly complex function of the sub's placement vis a vis reflecting surfaces and is hard to predict, so you have to set it by ear or room measurement.

I have this on my Velodyne sub and it is set to zero. Everything Marty said is the true in my experience. When I set the phase to 180, the subwoofer bass is much less and everything sounds a little bit out of tune. Whichever setting produces the most bass output should be the correct setting.
The first thing you should do is invert phase at your Rowland amp or speakers by reversing the + and - speaker leads to both channels. That will get your main speakers in correct polarity unless your preamplifier also inverts.

Once you do that, you won't have to invert the subwoofer's polarity, except that this would only be correct if your sub is located in the same horizontal plane as your main speakers... that's why they give you the Phase control.

So assuming your sub is somewhere else in the room, you would then adjust the phase control for maximum bass output while playing bass-heavy music. After that you would dial in the sub's volume level vs. the crossover frequency.

All this will take some time and experimenting if you are not familiar with the process. But once you nail the settings, the results will be well worth it.

MJ Acoustics makes subs where all the above parameters can be adjusted from the listening seat via remote control as you listen. They also offer 4 or 5 different programmable curves.

You can do the same with the Paradigm, but you'll need to go to the sub to make the adjustments and then sit back down at the listening seat to judge the results.
JWT, which Rowland amp do you own? In some cases, JRDG has adapters to change XLR input phase. G.