In the Church of St Dominic at the Dominican Priory (St Dominic's Parish and Dominican Priory) in Eagle Rock in the suburbs of Los Angeles (California), two triptychs painted by John Henry Rosen in 1951 have been preserved, originally forming the settings of two side altars (compiled from autopsy and photographs; dating based on signatures; no historical data or archival material available).

The triptychs, located in the side chapels, are framed in carved neo-Gothic dark wood frames with masquerade decoration overlapping the paintings. Both triptychs are built according to the same scheme: the rectangular central section, topped by a wooden masquerade canopy, is much higher and wider than the two rectangular side wings, also decorated with masquerade.

To the left is a triptych dedicated to Our Lady of the Rosary ('St Dominic receiving the rosary from Our Lady'). The central image shows Our Lady offering the rosary to St Dominic kneeling before her. Along the edge of the Virgin's mantle runs the following inscription: 'Mon cœur se recommende à vous - tout plein d'amour et de martyre', which is a slightly altered version of the words of a 16th-century madrigal attributed to Orlando di Lasso from 1560 (according to another version, it is an anonymous work written in the 19th century): "Mon cœur se recommende à vous - tout plein d'ennui et de martyre". At the feet of the Virgin Mary are the signature and date of the painting: 'Joannes H. | de Rosen | pinxit | a.d. MCMLI", and in front of St Dominic - a coat-of-arms cartouche with a running dog carrying a flaming torch in its mouth, the sign of the Dominicans (from Latin "Domini canes " - dogs of the Lord, which in turn is linked to the legend of St Dominic's mother. Dominic, who, before her son was born, had a dream according to which she carried in her womb "a dog holding a lit torch with which the whole world was set ablaze"). Both wings depict Marian visions: on the left, Our Lady of Guadalupe appearing to St Juan Diego, and on the right, three children kneeling before Our Lady of Fatima.

The second of the triptychs was dedicated to St Thomas Aquinas, the most important Dominican saint after St Dominic, the founder of the order. Here, all three paintings depict the events of the saint's life, according to the account of the 'Golden Legend' of James de Voragine. In the centre, St Thomas is depicted being restrained by angels, after having escaped the snare of a woman of ill manners, set by his family, who wanted to dissuade him from entering a monastery. This is how Father Peter Skarga described the event in his Lives of the Saints:

"Finally [...] they resorted to a stern and infernal work on him, for they repaired to a dishonest and lovely woman, so that, having secretly entered him, she might tempt him about his chastity; for whose loss his heart, enraptured with carnal pleasure, could gently be changed. When from her dress, venomous words and touching the young man felt an impulse to do evil, he called for Christ's help in his heart, and having called his name with his mouth, he jumped into the burning fire in the chimney, from where, having taken the main one, he struck the harlot with such anger that the frightened woman had to flee.

He closed the door behind her and, having made a cross for himself on the wall with the headboard, he fell on his face, weeping to the Lord and asking God to keep him clean. God, weeping, asked him to keep him pure and not let him fall like that; then, being long in prayer, he stopped and saw in his sleep that two angels were pulling down his loins with a girdle, saying: And he felt such a pain in his body that, coming to his senses, he cried out with a great voice, so that the guards rushed to him; but he saw this happening to him in his sleep, but he did not tell anyone (not before his death to his brother Reginald). From that time on he had the gift of holy chastity, and he guarded his white head of conversation very much, unless a spiritual need drew it out on him."

According to the above description, two angels restrained St Thomas, who was weakening, with ropes at the level of his loins. The latter has let go of the lit torch that now lies on the floor, presumably the same one with which he defended himself against the woman. To the right, just below the angel's feet, is the signature and date: "Joannes H. | de Rosen | pinx. | MCMLI."

The left wing shows St Thomas as a teacher, while the right wing shows him immersed in prayer in front of the crucifix.

In the chapel-oratory adjacent to the church of the former Dominican Sisters' convent (now abandoned), Rosen decorated the wings enclosing the niche with the crucifix in the main altar. They depict the personifications of the Four Elements as angels against a gold background, with their respective attributes and inscriptions: "terra" (earth - tree) and "aqua" (water - fish) - on the left wing - and "ignis" (fire - flame) and "aer" (air - bird) - on the right wing. Similarly framed personifications of Rosen's design - in the form of mosaics - adorn the facade of the chapel of St Catherine's Military School in Anaheim, where they flank the figure of St Thomas Aquinas.