As a food-conscious (ethics, food-as-fuel) gluten-free vegetarian, road travel can be a bit of a pain especially if the trip is long enough that I'll want food more than once. I've learned not to rely on the usual roadside places to stop for something resembling a meal. There are a few exceptions I've come across over the years, including SeQuential, Tally's Silver Spoon (a restaurant), Planet Ozone and others depending on where I'm driving and how long I'm mentally allowing for stops, detours, and anything that isn't absolutely necessary.
I've learned to pack trail mixes (often hand-mixed) and fresh fruits and veggies (as long as I'm not driving into California, where I have to prove my produce's citizenship). I've learned to buy tofu jerky (I need to try making this still) if I think I'm going to be short on protein and want something besides nuts. A friend of mine packs hard-boiled eggs -- I might do this if I didn't hate how eggs make me feel. Another friend swears by peanut butter, on pretty much anything. These are all good solutions, and if there's space, I'm in favor of packing yogurt in a cooler for stomach-calming calcium and plenty of protein.
But back to trail mixes: I like to select trail mixes for road trips because I don't buy them on a regular basis. They feel special. I can include chocolate if I want (always a nice treat, and quick sugar), dried fruits, nuts & seeds, or a variety of other options. They can -- and probably should -- consist of complex & simple carbs, plus protein and fats. GORP is a nice standby, except I haven't been buying peanuts recently because I'm tired of them. Instead, I've been using sunflower seeds or soynuts -- salted varieties of both, if you were wondering.
For an upcoming road trip, I decided to indulge in a trail mix with a variety of dried fruits (but primarily cranberries & raisins) and almonds. I'm going to throw in a handful of chocolate and call it good, then pack a couple of grown in the USA apples with stickers attached, corn tortillas + nut butter, and a couple of small containers of yogurt. And then I'm going to hope that's enough food for a several-day-total trip to a nearbyish city that will involve a lot of hiking and time outdoors. It's not as though I can't also opt into buying food there -- I'm sure I will, in fact (an avocado, some carrots) -- but in case that doesn't make sense for my schedule I want a back-up.