How to make round system?

Hello, I'm trying to make a round system for a game I'm working on. I just need help with the entire thing cause I have no idea where to begin. All I need help with is just a basic round system for now where there is an intermission countdown, a role assigning system that will give one player one role while everyone else will get a different role (so kinda like the killer and survivor roles in dead by daylight just instead randomized), and a system that will teleport the players from the lobby into the game using different scenes. If anyone can help me with a system like that it would be greatly appreciated.