In a small bowl, mix together the coffee, brown sugar, paprika, cayenne pepper, ginger, black pepper and cocoa, until well combined.
Put the pork rack in a large roasting tin and smear all over with the coffee marinade. Cover with foil and marinate in the fridge for at least 1 hour. Remove from the fridge and bring back to room temperature before roasting.
Preheat the oven to 220°C/fan 180°C/gas mark 7. Leave the foil on the pork and roast the ribs for 50 minutes. Remove the foil and cook for a further 10 minutes until the pork is nicely caramelised and cooked through with no pink remaining. Transfer to a carving board, scrape off any excess coffee rub and serve with the coleslaw on the side.