Make a part move with a player

hello, im trying to make effects that will be attached to the player “humanoidrootpart”, the effects im using are parts that are scripted to rotate and change size, but i cant find a way to attach the parts to the player and make them move with the player and rotates without breaking them, tried using weld and attachment and motor6d, but when i try to rotate the part using the parts cframe they rotate the player with it.
what is the best way to make a part rotate and change size with a script and in the same time attached and move with the player?