Are you using our standard robots.txt. If so, are there specific things you want to unblock? Just because something is blocked, it doesn't necessarily mean that is a bad thing, so its worth being careful what you edit
Just taken a look since you are on cloud. You appear to be using our optimised one. If you want to use your own instead, you can certainly do so if you are fully aware what you are doing
System>Site Promotion>Search engine optimisation>Crawl Management
Before deciding to do that, its very very likely what is being blocked, is for good reason. I would advise on having a read through this first