r2d2_bitmaps returning nothing

Hi All,
I found that some devices don't return any output after telnetting on 8080 and executing the command: r2d2_bitmaps like:

RokuHD (2000C)
Roku HD-XR (N1101)

Do you know of any workaround or something that must be done first to get info like:

Roku 2XD (3050) "Available memory 24147904 used 14852096 max 39000000"

thanks in advance