First of all, just in case, if you are not using it yet, you must install the excellent rails.vim from Tim Pope to work on Rohr with Wim. (Feel free to check out other plugins as well)
Allegedly, the likely reason you don't get html syntax highlighting is because the file is recognized by Vim as [eruby], not [html].
To make sure, open the erb file and type: set filetype?
It will display the file type identified by Vim.
To activate eruby and html5 syntax highlighting at the same time, you can open the erb file and type:
set filetype=eruby.html
I am not sure if multiple file types are 100% supported at the same time.
If this works, you can add the following line to your .vimrc so that the html filetype file is automatically added every time you open the * .erb file: autocmd BufRead,BufNewFile *.erb set filetype=eruby.html
Xavier T.
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