In some place I read that the queens KausalyA and Kaikeyi are mentioned chanting vedic mantras. For example they chanted when lord Rama and his brothers were born.
Also Sri Kaushalya used to offer oblations to Agnihotra fire when king Dasharatha was away.
I am looking for such references from the epic.
Valmiki Ramayana: Ayodhya Kanda - Sarga 20 answers your questions:
सा क्षौम वसना ह्ऱ्ष्टा नित्यम् व्रत परायणा |
अग्निम् जुहोति स्म तदा मन्त्रवत् क्ऱ्त मन्गला || २-२०-१५
Kausalya, who was interested to practise religious vows regularly was appearing auspiciously by wearing a white silk sari and gladly performing sacrificial ceremony in a sacred fire, by reciting vedic hymns. ~Source
In addition, Valmiki Ramayana: Ayodhya Kanda - Sarga 25 also contains such verses:
इति माल्यैः सुर गणान् गन्धैः च अपि यशस्विनी || २-२५-२६
स्तुतिभिः च अनुरूपाभिर् आनर्च आयत लोचना |
Uttering thus, the illustrious Kausalya having large eyes, worshipped troops of divinities with garlands , sandal paste and befitting hymns of praise.
ज्वलनम् समुपादाय ब्राह्मणेन महात्मना || २-२५-२७
हावयामास विधिना राममङ्गलकारणात् |
Duly procuring fire, she caused oblation to be poured into it, as per the direction of a high souled brahmana for the purpose of Rama's well- being .
इति पुत्रस्य शेषाश्च कृत्वा शिरसि भामिनी || २-२५-३६
गन्दांश्चापि समालभ्य राममायतलो चना |
ओषधीम् च अपि सिद्ध अर्थाम् विशल्य करणीम् शुभाम् || २-२५-३८
चकार रक्षाम् कौसल्या मन्त्रैः अभिजजाप च |
saying so, Kausalya, the large eyed proud woman placed some unbroken rice grains on her son's head, smeared varieties of sandal pastes over his body, fastened about his wrist by way of an amulet, a herb called Visalyakarani(so called because it helps in painlessly extracting an arrow stuck into one's body )which is efficacious and auspicious and muttered sacred hymns in order to enhance its virtue. ~Source
