ROTH contributions are shown on box 12 with a code AA or BB. That one in Box 14 is probably some type of employer plan, the client isnt deferring or contributing their own money into it.

How do I find the basis of a early distribution on a Form 1099-R with a code J in box 7 with no other information? Do I need to ask the client for more information? 

The 1099-R will have a box checkmarked for the type of retirement account this was distributed from. And look at the issuer name on the 1099-R, to see if that is the same as the employer plan account manager.

Only your client can tell you if they participate in Roth 401(k), 401(k), both. Example: it is possible your taxpayer contributes post-tax deductions to Roth 401(k) and the employer puts the match into the 401(k), because they are not allowed to put that into the Roth 401(k).

Might find your answer in 1040 IRS instructions