This Bob onboard ALLEZ has no roll tanks. and Leonard is absolutely correct why would you want to raise the center of gravity on a trawler. If you had the space for roll tanks why waste it when you an use the space for something else.
I have 4 ea 90 gallon water tanks total 360 gallons at 8 lbs per gal or 2,880 lbs of water for ballast and stabilization.they are on the center line of the boat on the keel two before the entrance to the V-berth forward cabin and the other two amidship LOW in the bilge between the engine rooms. Plus two 380 gallon fuel tanks one port one starboard ourboard. .total 760 gallons x 7 lbs per gal or 5,320 lbs. plenty of weight for stabilization, in proper places in the boat
safe cruising
Bob KovachMyrtle Beach, SCf