Roti is generally called roti or sometimes chapati in England, especially within communities familiar with South Asian cuisine. It may also be referred to as Indian flatbread.
While "tortilla" is sometimes used to describe similar flatbreads, it's more commonly associated with the Mexican version made from corn or wheat flour. In England, the term "roti" is widely understood, particularly in areas with a significant South Asian population. You'll find it labeled as "roti" in many restaurants and grocery stores.
Essentially, there isn't a different official name for roti in England; it largely retains its original name or the synonymous "chapati."