So if you Have not Fast in ramadan, due to any problem, and you died before completing those pending Fast (Roza) What should be done for this, Answer to this Question is clearly mentioned in this Hadees Mubarak.
Narrated ‘Aisha:
Allah’s Apostle said, “Whoever died and he ought to have fasted (the missed days of Ramadan) then his guardians must fast on his behalf.”
This Hadith Was taken From Sahih Bukhari
Book 31: Fasting
Hadith 173 (Volume 3)