If the theme you're referring to is the one on this blog: http://davidroccato.com/ then you're using Enterprise. Is that correct?
This is the showcase page for Enterprise,
and you'll see the various options on it. Included in it is the full-width template. That is just for pages, not for posts or for the home page.
Generally when one wants a blog with no sidebar, it's best to choose one with only one column or with theme options for sidebar or no-sidebar.I'm pretty sure that Enterprise does not have those options, but if you go to your dashboard, look at 'appearance' (on left side of dashboard), then on 'theme options' you'll see what is available to you for your theme. The alternative is to choose a different theme with the features you want:
You might also like to look on this site for the which themes do and do not have sidebars and footers (the area at the bottom of the page, often still referred to as a sidebar in some places):