Bunk trailers

[NOTHING ELSE MATTERS]

I'm looking to buy a 1990 V20 sport. I have a question for the guys with bunk trailers. The boat i saw has the original bunk trailer under it which have 3 wide rollers under the keel. The boat is not resting on those rollers nor are udjustable up or down. Does the boat has to rest also on those rollers? Is your boat resting on them, or just the bunks? The bunks on this trailer look like a 2X4 with the wider part(4) connecting with the boat.
Help please. Thanks.