Normally, an investment banker is responsible as structurer for bringing together the originator, the credit enhancer(s)(, the investors and other partners to a securitisation deal. It all works with the originator and helps in structuring deals.
The different panics to a securitisation deal have very different roles to play. In fact, first specialise in those areas in which they enjoy competitive advantage. The entire process is broke up into separate part with different parties specialising in origination of loans, raising funds from the capital markets, servicing of loans and so on. It is this kind of segmentation of market for that introduces several efficiencies securitisation is so often credited with.