my son is 8 m, we are in a king size bed, and he sleeps btwn my husband and I, he rolls so at times i wind up on the edge of the bed & even off. when he doesn't have one of us on the side of him I put a pillow near him, lightly touching him, he wont roll over it.
I'm not yet at the stage of putting the bed on the floor, but I plan to when he starts crawling & I will also put it against the wall, & have him sleep on the inside w/ a bumper, or pillows, or something else where the bed meets the wall.
my son also nurses every few hours, i found if i nurse him in the chair he will get a better feeding & sleep longer & not move around so much. also sometimes a walk or a few moments of rocking will soothe him w/o needing to nurse.
I sometimes have him in my arm, but that doesn't last so long, its uncomfortable for us both. usually we sleep on our sides, he;s facing me - so he can roll out if he likes & I have my arm above him.