Yes. Lord Rama had the knowledge of the Brahma shirastra. Not only Brahma Shirastra, he had the knowledge of many divine weapons. All these weapons were given by his teacher Brahmarshi Viśvāmitra.
दण्ड चक्रम् महत् दिव्यम् तव दास्यामि राघव || १-२७-४
धर्म चक्रम् ततो वीर काल चक्रम् तथैव च |
विष्णु चक्रम् तथा अति उग्रम् ऐन्द्रम् चक्रम् तथैव च || १-२७-५
वज्रम् अस्त्रम् नरश्रेष्ठ शैवम् शूलवरम् तथा |
अस्त्रम् ब्रह्मशिरः च एव ऐषीकम् अपि राघव || १-२७-६
ददामि ते महाबाहो ब्राह्मम् अस्त्रम् अनुत्तमम् |
daṇḍa cakram mahat divyam tava dāsyāmi rāghava || 1-27-4
dharma cakram tato vīra kāla cakram tathaiva ca |
viṣṇu cakram tathā ati ugram aindram cakram tathaiva ca || 1-27-5
vajram astram naraśreṣṭha śaivam śūlavaram tathā |
astram brahmaśiraḥ ca eva aiṣīkam api rāghava || 1-27-6
dadāmi te mahābāho brāhmam astram anuttamam |
"Raghava, I am going to give the highly divine Danda disc [Punisher disc]; next, oh, best one among men, Dharma disc [Virtue-disc,] and like that kaala disc [Time-disc]; then oh, brave one, Vishnu disc; similarly oh, dextrous Rama, Indra disc and Thunderbolt missile; the best trident pertaining to Shiva; the missile called Brahma-shira [Brahma-crest]; the missile called the Aishiika missile [Grass-Blade missile,] and that way oh, Raghava, I am going to give the unexcelled and highly formidable missile called Brahma missile.
Indrajeet obtained this weapon by a penance. It is mentioned in the 85th sarga of YuddhaKanda.
तेन वीरेण तपसा वरदानात्स्वयंभुवः |
अस्त्रं ब्रह्मशिरः प्राप्तं कामगाश्च तुरंगमाः || ६-८५-१२
tena vīreṇa tapasā varadānātsvayaṃbhuvaḥ |
astraṃ brahmaśiraḥ prāptaṃ kāmagāśca turaṃgamāḥ || 6-85-12
By his penance, Indrajit obtained a weapon called Brahmashira, by way of a gift from Brahma and also horses, which are coursing at his will.
The missiles possessed by Rama are given here.
The knowledge of this weapon was given to Arjuna and Aśvatthāma by Dronacharya. Teacher of Dronacharya is a sage named Agnivesha. Drona learnt it from him.
From this chapter of Sambhava Parva, Adi Parva,
One day, Drona, addressing Arjuna before the assembled Kaurava princes, said, 'There was a disciple of Agastya in the science of arms called Agnivesha. He was my preceptor and I, his disciple. By ascetic merit I obtained from him a weapon called Brahmasira which could never be futile and which was like unto thunder itself, capable of consuming the whole earth.
Now, Agnivesha was a disciple of Agastya in the science of arms. So, it is very much possible that Agastya was also knowledgeable of the astra.
Therefore the possible warriors with knowledge of the weapon would be
- Bhishma (highly possible).