Robots.txt cannot be used to "make" robots do anything. It is used to ask robots not to fetch certain parts of your Web site such as membership signup pages, scripts that take an action you would not want a robot to trigger, etc.
Compliant robots will honor your requests, while e-mail address harvesters and site scrapers won't. For the latter, you can take stronger steps by using server-side access controls (e.g. .htaccess) and/or server-side scripting.
If you want robots to visit your site, then you need to get other Web sites to link to your site. Robots follow the links that they find on sites that they already know about, and find more sites. "Search engine submission" as practiced in the 90s is dead, and that's why the similarly-titled forum here at WebmasterWorld is deprecated.
To get more love from the search engines, get more links from other topically-related sites with link text that is relevant to their site and to yours.