We feed our rabbits a ration of pellets twice a day and allow them to eat unlimited amounts of grass hay that is constantly available.
From personal experience, rabbits given a free feed diet of pellets will eventually gain weight which can lead to all kinds of problems, especially for pregnant does. We do however give does and their litters free feed once the young are out of the nest box.
Veggies and other treats can be given occasionally, but in moderation. In general, vegies are healthier for rabbits than fruits are and of course things like parsley, lavender, and dandelions can be very good for your rabbits diet.
As long as you're giving your rabbit pellets, it will be fine, as pellets contain all the right ingredients and right amounts for all the nutrients rabbits would naturally find in the wild. Brood, show, and pet rabbits are fed differently balanced pellet diets, but in all, pellets are the best choice for your rabbit's primary food source.
As mentioned above, we also give our rabbits unlimited grass hay. This simply gives the rabbits something to munch on when they do get hungry between feedings and is low in nutrients and calories so it doesn't upset their nutritional balance. It also aids in digestion for them as well.