You either group up yourselves or you have to be REALLY careful when farming lanes and whatnot, you can't go to far if you know they are rollin around in a gank squad, but usually if you play defensive long enough they will get tired of it and spread out themselves, giving you an opportunity to gank them in return. Sometimes baiting them out to try and gank one person can give opportunities to catch them more spread out.

Buy wards. Place them in the river and jungle. Ricefest in peace until you see a red dot on your minimap, then recall.