Nice assortment of plants to start your new hobby with. Very nice of the guy to have gifted you with those free plants. The rollinia is said to be one of the best annona species and it taste like lemon meringue pie. The pitaya is very refreshing and sweet, well this depends on the variety it is. Some are less sweet than other and have watery flavor. It's best to severed them cold out of the fridge chilled. Black sapote is sweet and the inside flesh of fully ripen fruits look like chocolate pudding, however, doesn't actually taste like chocolate at all. Sorry, these are just what I read about them and haven't actually tasted any of the fruits from the variety of trees you have, except mangoes. Mangoes are available everywhere and there are so many varieties, with all kind of different flavor profiles and texture.