I love making nori rolls as they are easy to take with me when I travel or for lunch at work.
I fry thin omelets from eggs with some spices (such as turmeric, wasabi, black pepper, chili, Italian herbs or fresh herbs. You can also add a little garlic powder) and cut those in half.
Place the half (cooled down) omelet on the nori sheet. Then on the middle of the omelet place your filling.
Your filling can be whatever you like: salad, avocado, greens like watercress, sprouts, smoked salmon, tuna etc. I have even filled them with left over stir fried vegetables.
Make sure not to over fill them as they will tear and also watch that your filling is not wet (moist is still OK I find). Gently roll to a close and wet the end of the nori sheet so it will stick.
You can cut them in half or in 4 pieces. You can be super creative in combinations with this. I once cooked some fresh salmon with lots of wasabi powder into the omelet and then filled it with a watercress salad mix and avocado.