Response curves for Roman’s HLTDS overlaid with typical spectra of SNe Ia at three different redshifts: z = 1, z = 2, and z = 4. The Wide tier of HLTDS will use four filters: F062/R, F087/Z, F106/Y, and F129/J, while the Deep tier will use the filters F106/Y, F129/J, F158/H, and F184/F. From the figure it is evident that HLTDS, particularly the Deep tier, is well-suited for discovering high-redshift SN Ia, even beyond z = 4.