You can get the PLS equivalent of R-squared* for dependent variables, this is the value shown in Output 92.1.1 here: https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_pls_examples01.htm
If you really need RMSE I think you could calculate the RMSE if you know the R-squared and total variation in Y, or from the residuals in Y.
* — if there is more than one dependent variable, this quantity is computed across all of the dependent variables.
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Paige Miller