"I am planning to rotate my next year plants and I want to make sure I bring the right plants for the future crop." I don't understand what you mean by this??

Where in Canada are you located Lana?

Any cover crop is better than no cover crop. And it really doesn't matter too much what you select as most cover crops are leguminous, so will help add nitrogen to the soil as well the green biomass. (aka green manure).

Essentially you can choose between winter killed cover crops or winter hardy cover crops. Or a mixture of the two types, which is my preference. Sow as soon as your summer garden is harvested and be sure to turn the cover crop into the soil before it flowers or a month or so before you intend to plant.