Here's what I would do:
-Buy a couple rotisserie chickens
-Bag of nice salad greens
-Loaf of bread
-Favorite dressings
-Cheese
-Salsa
-Tortillas
-Watermelon, grapes
-Veggies
and so on, then do things like:
-rotisserie chicken salad
-quesadillas
-chicken tacos
-breakfast burritoes with your bacon and eggs and the cheese
-grilled cheese
In other words, make sure anything you buy you can use for more than one thing. I'm a huge fan of spaghetti, but it might feel a little hot and heavy at that time of year. (Just like BirdsOfPrey suggested above)
And/OR:
You could also just choose to pick something up like a frozen pizza or lasagna for one night; soooo much cheaper still than eating at the World, but easy.
I'd bring ziploc bags in your suitcase, since they are good for so many things anyway, and use them for leftovers rather than containers. You can always put a gallon ziploc over a plate or bowl of leftovers if you don't want to transfer it.
Cube a bunch of watermelon and keep it for folks to snack on all week.
I think cool and salty things taste great when it's really hot, so I might pick up something like some veggies, hummus, pita and feta cheese, and just have that for dinner-my kids would eat it, it's healthy, and it makes great lunches later. Feta watermelon salad is fabulous

. Feta tossed with spaghetti noodles, tomatoes, green onions, and olives, maybe some chicken (sub any cheese you want) is a super easy, yummy entree.
I wouldn't go to the trouble of picking up a roaster or anything for just one meal. Think of things you can do in a pot or smaller pan in the stove, or buy your meat roasted already.