TOAST is based on cordova and unfortunately you will have to deal with CSS, JS and HTML. But you will get lot of extra functionalities to build a multiplatform apps due the main point of TOAST is to act as a proxy between your app and the TV, so every operation in TOAST is translated to the correct system function. You can check the TOAST wiki to get a complete list of methods and its compatibility with the supported platforms (browser, LG webos, Samsung Tizen, Samsung Legacy (orsay))
A more formal framework for Tizen would be CAPH:
CAPH is a Web UI framework for TV. Develop High Performance Web Application Easily and Quickly. CAPH consists of below modules.
Key Navigation
Scrollable List and Grid
UI Components : Button, Radio Button, Toggle Button, Checkbox, Input, Dialog, Context Menu, Dropdown Menu
Touch feature : Pan, Tap and Double Tap. (from CAPH 3.1)
Please find more info about CAPH here