In addition to religious commissions, Roper created a wide variety of sculptures which were sold privately and to corporate bodies.

[5] Many of Roper's early commissions stemmed from the need to repair places of worship after they had suffered bomb damage during World War II.

Over his career Roper worked in wood, stone and bronze,[18] but many of his ecclesiastical commissions, as well as his musical fountains and water clocks, were cast in aluminium.

He became interested in aluminium in the 1950s; the Stations of the Cross for St Martin's in Roath, Cardiff, completed in 1959, were an early example of his religious art in the metal.

[19] His work for Christ Church in Roath (1964)[20] may have been his first commission using the lost-polystyrene method, a casting process recognisable by the texture of the metal, as the pitted nature of the expanded polystyrene remains visible.

[22] Having his own home foundry also kept costs down and allowed for a very direct relationship with the finished work – "conception, creation and casting became one continuous process" he told the Church Times in 1994.

Roper is credited with inventing the process[1][5] although other artists were developing this technique at the same time, including the sculptor Geoffrey Clarke,[23] working in East Anglia.

[22] "That's the important thing about them", Roper notes in the documentary Look Stranger, "they are primarily sculpture, so at night when there's no light coming in from outside we have an interesting relief.

"[10] An example can be seen in Virgin and Child, a window in St Augustine's in Rumney, Cardiff; Peter Leech in The Religious Art of Frank Roper describes the "literally outstanding" metal "delineat[ing] the figure emerging from a profundity of deep blue glass".

[27] Roper's window depicting the Resurrection in St Mary's, Talbenny, Pembrokeshire, one of three in that church, is an example of his use of small chunks of knapped glass fixed to the surface in order to catch and disperse light.