I think I've answered my question, but in case anyone else happens upon this post, here it is.
Looking at the output file from running the 3dDeconvolve, there is the following text to help you a long your way. It appears it spits out the exact 3dREMLfit command you should use for the particular subject. For instance:
+ ========= Things you can do with the matrix file =========
++ (a) Linear regression with ARMA(1,1) modeling of serial correlation:
3dREMLfit -matrix X.xmat_Interference.1D \
-input "pb04.sub-102.r01.blur+orig.HEAD pb04.sub-102.r02.blur+orig.HEAD pb04.sub-102.r03.blur+orig.HEAD pb04.sub-102.r04.blur+orig.HEAD" \
-mask mask_anat.sub-102+orig -tout -Rbuck stats_Interference.sub-102_REML -Rvar stats_Interference.sub-102_REMLvar \
-Rfitts fitts_Interference.sub-102_REML -Rerrts errts_Interference.sub-102_REML -verb
++ N.B.: 3dREMLfit command above written to file stats_Interference.REML_cmd