Place a sheet of cling film on a work surface. Lay the smoked salmon slices in a rectangle about 20cm x 10cm/8in x 4in, overlapping the slices slightly so that there are no gaps.
Spread the cream cheese over the smoked salmon and sprinkle with the sliced spring onions, chopped dill and cayenne pepper.
Roll the roulade up lengthways and twist the cling film at the ends, so it looks like a Christmas cracker. Chill in the fridge for an hour, if possible.
Slice the roulade into 2cm/¾in slices and arrange on a serving platter. Garnish with dill sprigs and serve.