First, none of these dishes is particularly spicy - hot sauces are here at the restaurant to add, or (obviously) add hot sauce at home to preferred spice level.
The only dish that requires some reheating skill is the Vada Pav (potato patty in a soft roll). The patty should be heated up in a toaster oven, regular oven, or in a skillet with a little oil (be careful about it breaking up if you do this way). Split the roll. Then, if you want a little heat, put the hot chutney on (it's not super spicy) and make the now heated patty into a sandwich. You could also microwave the roll for 10 seconds to get that warm if you so desire. Eat the salad cold as a relish.
The rotis I would heat up like tortillas - ie wrapped in a damp paper towel in the microwave. You could also put them in a skillet, they just won't necessarily end up soft. Either way, I'd definitely recommend heating before using.
The stews, sauces, veggies are all in microwaveable containers. Or you can use a saucepan. Every one of them tastes much much better warm. Except the raita, don't heat the raita.
The Bay Leaf Pudding tastes good either warm or cold. I prefer warm, myself.