Distributions from a Roth IRA will have code J, T or Q. Distributions from a traditional IRA will have code 1, 2, 4, or 7.
In general, there is not a way to tell if a Form 1099-R is reporting a distribution from a Roth IRA or a Traditional IRA.
Some of the distribution codes used can indicate one type of account or the other, but there is not a place on the form that will indicate the type of account. You may need to contact the payer for more information.
Take a look at the information below for a list of the distribution codes in case that is helpful.
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What if the 1099 has a number and a letter next to each other
If the code in box 7 includes code J, T or Q, the distribution is from a Roth IRA.
If the code in box 7 does not include code J, T or Q but the IRA/SEP/SIMPLE box next to box 7 is marked, the distribution is from a traditional IRA.
If neither of the above applies, the distribution is not from either kind of IRA.