Well, there are the Vinland sagas, and while the events in those are pretty wild, the mere existence of those suggests that some actualy did return. They where recorded sometime between 1220 and 1280 so even though this was well after the fact (about 200 years) it's still before the age of exploration.
Edit: As for the tomato question, the sagas suggests that no or very little friendly interaction with the natives took place, so no real trade or exchange of knowledge. These where not full on atlantic voyages but mostly near coastal areas of Greenland and what is now northen Canada. I kinda doubt that the natives would be growing tomatoes that far north anyway. Though, they did claim to find grapes, which suggests that they ventured a fair bit south as well...
Edit: As for the tomato question, the sagas suggests that no or very little friendly interaction with the natives took place, so no real trade or exchange of knowledge. These where not full on atlantic voyages but mostly near coastal areas of Greenland and what is now northen Canada. I kinda doubt that the natives would be growing tomatoes that far north anyway. Though, they did claim to find grapes, which suggests that they ventured a fair bit south as well...