A reservoir for use in a wearable infusion device includes a substantially rigid base having a perimeter, a substantially rigid top having a perimeter, and a flexible rolling diaphragm between the base and the top. The diaphragm has an outer perimeter sealed along the perimeter of the base and an inner perimeter sealed along the perimeter of the top. The diaphragm is arranged to dispose the top and the base immediately adjacent each other when the reservoir is empty and to dispose the top and the base in spaced apart relation when the reservoir is full.
