A support apparatus (e.g., stretcher, back board, etc.) with double roller assembly. The apparatus includes a main frame, a first housing containing at least one wheel (e.g., gear, pulley, sprocket, roller) around which a first sheet and/or a second sheet is coiled. The opposite ends of the sheets are coupled to vertically- and horizontally-displaced lead and trail rollers in the double roller assembly, one sheet for each roller. The apparatus further includes a second housing containing at least one wheel around which a chain or belt is disposed. One or both ends of the chain/belt is coupled to the double roller assembly. In operation, a patient is positioned within the main frame, and the sheets extend underneath the patient. The belt/chain mechanism can also help urge extension of the sheets. When the sheets are fully extended underneath the patient, the patient is fully supported and can be transported.