Cook the sausages according to the instructions on the packet. Set aside to cool, then slice in half.
Meanwhile, slice the ciabatta rolls in half. Rub each with a little olive oil and the cut side of the garlic clove. Heat a griddle pan over a medium heat, then add the ciabatta slices, crust side up, and toast until golden. Set aside.
Mix the mayonnaise with the pesto until well combined. Spread on to one half of each ciabatta roll. Layer each with the sundried tomatoes and slices of mozzarella. Place under a preheated grill until the mozzarella begins to melt.
Make the sandwiches by putting 3 sausage halves on each slice, along with a few rocket leaves. Top with the remaining ciabatta halves and serve.