You will be responsible for the bulk of the web design, UI / UX, wireframing, and Graphic Design tasks that come through the door. It's important to note that you will be the first person on the design team so you'll have to be comfortable being the go-to person for anything related to design.
While you will start as the only person in the design team they will look to increase this over time and there will be opportunities to move up within the company to positions depending on what you're looking for. The client expects there to be a Creative Director role after the team has grown.