1) Where are you located?
2) How has your weather been?
3) How often/how much do you water?
4) What kind of fertilizer/how much/how often?

I am in California, about 50 miles north of San Francisco. It's been hot, in the 90's during the day. It cools off at night, though, in the low 50's. I water usually once a day, but if the dirt is still moist then I skip a day. I use Alaska Fish Fertilizer 511 (from Walmart). I've only used it a few times, 2 Tblsp/1 gallon of water. I'm pretty clueless when it comes to fertilizing, I read somewhere that I should use the fish fertilizer because it's organic. I've never had any problems growing tomatoes in the past 3 years since I moved into my house, except for the hornworms that showed up a couple of years ago. That is why I decided to give container-gardening a try. I'm not having very good luck, it seems! :-)

The leaf roll could just be physiological, meaning just something that happens as a response to stresses like hot weather, underwatering, overwatering, etc. It sounds like your watering regimen is fine.

Based on the information you provided, the most likely explanation is that the leaves turning yellow and purple because of a nutrient deficiency. Alaska Fish Fertilizer has nitrogen (N), but not much phosphorus (P) or potassium (K), and I have no idea whether it has many of the other nutrients, such as Mg and Ca, which tomatoes need. It's a fine fertilizer for leafy green veg, or for tomato plants when they're young before they start to bloom, but once they start to flower and fruit, they'll need more P and K than N. I would suggest you get a liquid fertilizer specifically for tomatoes or at least for fruiting vegetables, and try that and see whether your plant improves.

There is a chance that your plant could have a virus, though. Keep a close eye on new growth. If it appears very curly and distorted and/or develops fat, purple veins or turns very purple on the underside of the leaves despite fertilizing with a tomato-appropriate fertilizer, and if the newer flowers start looking weird, it probably has a virus vectored by whatever pest caused the damage in the first pic (looks like leafhopper damage to me, and based on that and your location, I would think that Beet Curly Top Virus would be a top culprit). If it turns out that your plant does have a virus, it should be pulled and discarded. Here's a fact sheet on it with some photos which can give you an idea what to look for. Note that the distortion with a virus will be more dramatic, not just the rolled leaf edges you have now. Your local county extension should be able to help if you're unsure about a diagnosis.

But don't panic yet. I think it's more likely to be a nutritional issue + heat-related stress.

Thank you so much, I really appreciate your help! I'm off to the nursery to find some fertilizer. I'm so happy I don't have to freak out & that I don't have to pull my tomatoes today, because it's very hot! Again much thanks, have a great day.