According to the traditional Japanese religious sects, Mahayana sutras such as Hannya-kyo, the Nirvana sutra and the Hokke-kyo, which was considered to have been written in a later age by other sects, are not rootless because it's possible for disciples of existent religious organizations to succeed and develop their master's dharma.
日本の伝統教団では、師の教義を弟子が継承し発展させることは、生きた教団である以上あり得ることから、法華経をはじめ般若経、大般涅槃経など後世の成立とされる大乗経典は根無し草の如き存在ではない。