Your role is finding solutions to problems. Some things you might consider are how to build houses that can withstand high winds? How to make sure your town is lit at night?
Tip: Try using Redstone to build a circuit. You might help a business owner build an automatic door to her shop.
Your role is to build farms and supply food to the citizens of your town. You might consider what kinds of food can feed the most people, what food can grow with less light each day, and how you might raise livestock.
Your role is to break stuff... or at least come up with ideas to test the strength of claims the others are making. How will we know if a building can really withstand high winds?
Your role is to understand the cause and effect of Earth's conditions after the moon has disappeared. You are extremely important in helping your teammates understand the implications of their respective settlement designs.
Your role is to determine how it all fits together. You need to make sure everyone has access to food and water. How close should people live together? Where do you put roads?
Your role is to think of businesses that will be essential to the members of your settlement. How will you exchange goods and services? How to balance supply and demand?