Maybe. If they have a RESTful api or you can find examples online of http get/post requests for the Roku, you can try them using VC's various scrape actions.
If you know your Roku's IP address, you could enter it in the command below where indicated, and try the following command.
e.g. Say one of the following: Go home; go right; go left; go up; go down; go back; Roku select; Roku play
(This is based on a super quick search I did, so it's a giant shot in the dark.)
<?xml version="1.0" encoding="utf-16"?>
<!--VoxCommando 2.1.4.5-->
<command id="775" name="Go {1}" enabled="true" alwaysOn="False" confirm="False" requiredConfidence="0" loop="False" loopDelay="0" loopMax="0" description="">
<action>
<cmdType>Scrape.Post</cmdType>
<params>
<param>http://YOUR_ROKU_IPADDRESS:8060/keypress/{1}</param>
<param />
<param />
<param />
<param>text/html</param>
</params>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>OSD.ShowText</cmdType>
<params>
<param>{1}.</param>
</params>
<cmdRepeat>1</cmdRepeat>
</action>
<phrase>Go, Roku</phrase>
<payloadList>Home, Left, Right, Down, Up, Back, Play, Select</payloadList>
</command>