Thomas spent many nights on the roof ever since his parents had shipped him off to Pallet Town. It was just one of his things. He and Ralts would spend many nights studying the stars, and many days would be spent in his room doing research on a plethora of different subjects. His grandparents never really paid him any mind. Not that they were neglectful or anything, but he was old enough and self-sufficient enough that they never needed to do much for him.
It was on a normal day that he lay upon the roof of his home, tossing rocks off of the edge and letting Ralts use her psychic powers to launch them at speed into the tall grass of Route 1. He had found several weeks ago that occasionally it would scare wild Pokemon out of the grass, and let him observe them through the binoculars he kept in a box on the roof. In doing, he noticed a large group of people gathering around the entrance to Route 1. Eventually, curiosity got the better of him and he returned his friend to her Premium Ball before tucking it into his pocket and clamoring down from the roof.
He didn't try to hide his approach, but he took it slow and when he stopped he was still a fair ten yards away. Reaching into his pocket, he palmed the ball before crossing his arms and listening to all of the people around him. He watched the battle that wasn't much of a battle, took in the sights of all the different Pokemon around him, and generally just waited to either be confronted or left to observe one of his favorite pastimes; observing.