Rollup not recognized as a command when running grunt

Running a grunt --force on Windows results in

Running "shell:command" (shell) task
'rollup' is not recognized as an internal or external command,
operable program or batch file.
Warning: Command failed: rollup -c
'rollup' is not recognized as an internal or external command,
operable program or batch file.
 Used --force, continuing.

Could it be a dependency issue?

[nheminger]

Running npm install -g rollup fixes the problem. Possible to fix the dependencies or add documentation to the readme instructions so those running grunt will have it work?

[ecaldwell]

I think the solution is to specify the path to node_modules in the shell command. You can see this in my Gruntfile on #178.

Now the command looks like this rollup: "<%= node_modules %>rollup -c" where node_modules is defined earlier in the config as .\\node_modules\\.bin\\.

I tried a variety of combinations to get this to execute properly and this was the only way that worked. Unfortunately, the escaped backslashes are necessary—using forward slashes caused errors. It would be good for someone on a Unix machine to verify if this works.