An unskilled or semiskilled labourer especially in an oil field or refinery. (Merriam – Webster)
A roustabout is a unskilled worker, especially one who works in a port or at an oil well. (Collins Dictionary)
A person whose job involved heavy unskilled work. (Cambridge Dictionary)
An unskilled or casual labourer. (Oxford Dictionaries)
What Does a Roustabout Do in the Oilfields?
A roustabout throwing a freshly shorn fleece onto a wool table for skirting and classing.