Sehri is not compulsory either during fasts of Ramadhan or Nafl fasts (Rozas), although it is a great Sunnah and a source of great blessings and we should have it.

Since it isn't compulsory for any kinds of fasts, your Roza will be valid if you skip Sehri but you would be deprived of blessings and following the Sunnah of our beloved Rasul-ullah (Sallaho Alaihe Wassallam) so a person should try their best to have Sehri.