This work presents the first search for RR Lyrae stars (RRLs) in four of the ultrafaint systems imaged by the Dark Energy Survey using SOAR/Goodman and Blanco/DECam imagers. We have detected two RRLs in the field of GrusI, none in Kim2, one in PhoenixII, and four in GrusII. With the detection of these stars, we accurately determine the distance moduli for these ultrafaint dwarf satellite galaxies; 0=20.510.10mag (D=1276kpc) for GrusI and 0=20.010.10mag (D=1005kpc) for PhoenixII. These measurements are larger than previous estimations by Koposov etal. and Bechtol etal., implying larger physical sizes; 5percent for GrusI and 33percent for PhoenixII. For GrusII, of the four RRLs detected, one is consistent with being a member of the galactic halo (D=241kpc, 0=16.860.10mag), another is at D=552kpc (0=18.710.10mag), which we associate with GrusII, and the two remaining at D=432kpc (0=18.170.10mag). Moreover, the appearance of a subtle red horizontal branch in the colourmagnitude diagram of GrusII at the same brightness level of the latter two RRLs, which are at the same distance and in the same region, suggests that a more metal-rich system may be located in front of GrusII. The most plausible scenario is the association of these stars with the Chenab/Orphan Stream. Finally, we performed a comprehensive and updated analysis of the number of RRLs in dwarf galaxies. This allows us to predict that the method of finding new ultrafaint dwarf galaxies using two or more clumped RRLs will work only for systems brighter than MV 6mag.