There are many great schools in Rohini. But, if you are looking for convent schools precisely, then you could go for these convent schools -
Lancer's Convent
Queen Mary's Convent School
St. Xavier School
I have heard some great reviews about these schools and their academic results in recent times. You might also want to consider Bal Bharti Public School and Aadharshila Vidyapeeth for overall improvement in performance (both academic and co-curricular).