Bearing in mind that Eloquent does not have support for composite primary keys , I recommend that you raise the structure of your database in a different way to save yourself headaches.
Assuming (I do not know if it will be like that, but it can be adapted) that a round has several rolls (draws) and a roll belongs to a player, you can build some relationships:
player 1 - N draw (player hasMany draws, draw belongsTo player)
round 1 - N draw (round hasMany draws, draw belongsTo round)
Provide more information about the relationships you want to make so that I can show you a more complex example.
It's tennis ... - a Draw has many players and many rounds. - A player will be in many draws and many rounds. - A round will be in many draws and will have many players.
draw M - N player (player belongsToMany draw, draw belongsToMany player)
draw M - N round (draw belongsToMany round, round belongsToMany draw)
player M - N round (player belongsToMany round, round belongsToMany player)
There are three relationships with the pivot table between them, but more information is needed, since you are using a ternary but you have not provided enough details to know what you are trying to do.