Yes.
Mathematicians have a career in every field.
Of course you can get a job in ISRO or BARC after completing M.sc in Mathematics.
You can apply for posts like, Scientist/Engineer posts.
Qualification :
The applicant having an M.sc Degree with a first Class i,e. an aggregate minimum of 65% (Average of all semesters) or CGPA/CPI grading of 6.5 on a 10 scale or equivalent from a recognized university are eligible.