Now this was the first time I had piped a rosette so my apologies, but I used wilton star tip 1M, started on the right hand edge of the cake and then ...
Start with your favourite cupcake, make sure it is totally cooled before you decorate it.
Colour some readymade icing orange with gel food colour and roll a lump of it into a ball. Using a cocktail stick make some light indentations around the orange ball so that it looks like the segments of a pumpkin. Then colour a tiny bit of readymade icing with black gel food colour. Shape two tiny black triangles, a tiny circle and a tiny crescent and then use a cocktail stick to position them on your pumpkin so they look like a face, they should stick on themselves but use a little water if they need some help.