After a year's research I've found a method to get Lenovo A319 Rockstar's ROM for flashing.
I've used Fidler and tunneled the mobile traffic into it. From there, I've got the download URL of the ROM which is signed by Lenovo's original certifica...
phonedl. ota .lenovomm.com/ dls/v6/A319_ROW_DS_S319_161222_ WCED3B8707.zip
Download it, place on sdcard , reboot into recovery mode and flash from sdcard....