When you enter the venue, you'll probably notice the loud sound of controllers which may sound like someone button mashing. When you go in to look at everyone playing, assuming you aren't early, all available setups are taken for friendlies. This is the annoying part: meeting new people and joining a round robin. However, this must be done as fast as possible, as it is the best practice you will ever have. That being said, play as many friendlies as possible.
You'll start to learn familiar faces as you play and be more accustomed to other players. These will pretty much be your friends once you attend more tournaments in the area that they're going to. You should constantly play with them, and make sure you have a variety of players who all use different characters, as you will be more accustomed to the meta and improve over most matchups that you will face commonly (like Fox or Falcon).
As of playing Roy, you will definitely have a tough time in friendlies and even bracket, as Roy has his limitations that regardless how good you are will make every set a struggle. Honestly, play someone like Marth as he is virtually better in every way and makes your sets much easier. But, if you continue to main Roy or even use him as a real secondary, you'll have to play a lot to learn how to deal with his weaknesses against the meta which can be very limiting.
In pools and potentially brackets, you will probably lose your cool and your mindset which will negatively impact your performance. Try your hardest to keep calm and play how you normally would against CPU and in friendlies, and don't focus TOO hard as you will lose your flow and train of thought and reactions.
