have you googled "robots.txt generator"? you will find a good selection of tools for you to generate this file.
you can do two things for robot.txt first visit here http://www.mcanerin.com/en/search-engine/robots-txt.asp or else you can check the IBP tool , which has a lot of things to do. in fact with the IBP tool you can do the simulation check of it's own robot.txt file.
No any blog allow user robots.txt file. Blogger by default allow all pages of blogs. robots.txt file used. If you didn't want page crawl by crawler then we use robots.txt file.
robots.txt just a plain text file. you can use notepad to "generate" it. what you really need to know is the standard how to disallow the robots and which part of your site that need to be kept out from robots. if you want to allow all of your site to all robots, just put in your robots.txt: User-agent: * Disallow:
use Google Webmaster Tools to generate robets txt that is a best tool or you can google for other tools it is vest simple.
It would be better if you can describe the specific problems you are facing in robots.txt so that we can review the same and could provide you a solution.