Yes, room service is included. You'll have a "thingie" to hang on your door indicating what you'd like for breakfast ... coffee, tea, milk, baked goods, juice, cereal, fruit sorts of things. Makes a great alarm clock as you designate the delivery time.
A tip isn't required, but we tip $1 pp for the continental breakfast service.
You can order room service pretty much any time of the day from a rather limited sandwich/salad kind of menu. If you order soda, there will be an extra charge.
If your ship features NCL's signature alternative restaurant, LeBistro, don't miss it. Very enjoyable for a minimal surcharge.