RadTileList offers responsive design capabilities that let it scroll downward on smaller screens: http://www.telerik.com/help/aspnet-ajax/tilelist-responsive-layout.html. You can also see the CSS that does this here: http://www.telerik.com/help/aspnet-ajax/tilelist-css-for-responsive-layout-of-radtilelist-and-tiles.html. You can consider modifying them to match your needs (e.g., change the media queries) and adding the new CSS to the page so it overrides the built-in rules.
Another option I can suggest is generating the standalone tiles you need (http://demos.telerik.com/aspnet-ajax/tilelist/examples/standalonetiles/defaultcs.aspx) and adding them to an arbitrary container. They are simple div elements with display: inline-block and float: left from layout standpoint so their container can scroll according to your layout.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.