from memory meats cooked past 60 degrees C right thru and eaten hot is generally thought safe because that heat kills the bacterias.
I don't know about other bacteria, but I believe it's 70C for listeria.

On the sushi thing, if you cooked the rice and chicken fresh and refrigerated them straight away they should be fine as long as you use them within 24 hours. However, having said that, I'm super-paranoid and wouldn't eat either of those cold.

For the tea, there's so many conflicting opinions. Read up on it and decide for yourself what you believe. I don't recall hearing of any issues with plain black tea (other than the caffeine), but I'm not an expert by any means.

For the leftover roast meat, I'd just microwave it before putting it in the sandwich to make sure it's piping hot the whole way through. Again, use within 24 hours of original cooking.

And as for the greasy food... I've been so bad with that. DH & I eat too much take away and, with the restricted options (based on who I trust to sell freshly-made hot meals), I have to admit that fish & chips and pizza do make it to the top of our list too often.