Here is what I do and it works for me. I roll my quilt width wise, then measure the length of the quilt. I make a long tube type bag with an opening. I measure the width to give me plenty of room to fit the quilt in the bag. I label each bag so I know what's in the bag. Then it goes on top of a bunk bed which is not used very often at all!
I make a string to fit the bag opening out of selvages I've cut from fabric. I double the selvages and sew with my serger. Then I string the selvage through the opening of the bag and tie a bow. Is that clear as mud?