To do this, refer to your pasta package, the time will be half of the shortest recommended cooking time, rounded down to nearest minute. (101cookbooks.com)
All you have to do is select the type of roast, the weight, and how done you would like it, and it gives you a timer with the recommended cooking time. (curiouscuisiniere.com)
Add your pasta and simmer for whatever the recommended cooking time is. (supergoldenbakes.com)