I do not know how you have set out your tables or the full extend of what you want to do or you level of knowledge of access or vba so if the following is of no use to you i am sorry.
But a way to do what you want would be

Create a list box which can be multiply selected which contains the names of the students with the bound column being the students ID.

Select all the students in this this list box that you want added to the roster table, loop through all the selected in the list box and create a dynamic SQL string to add each student to the roster table and execute it, you can also add any other infomation to the table at this time by including it in the SQL string. You could also use a DAO Recordset and append the data this way.