Etia, 19, has most recently played his football at Central Midlands League side Ollerton Town, scoring 11 goals in 29 appearances.
The former Rotherham U18's player has experience in the Northern Premier League, featuring for Brighouse Town and Sheffield FC.
Joining him at the Hurst Cross Stadium is centre-forward Kevin Spinelli.
Spinelli, 19, is a former Accrington Stanley Academy prospect who joins the Robins after leaving the League One side in July.
The athletic striker featured for Radcliffe and Bamber Bridge last season, scoring twice in 7 outings for the Boro and once in 7 appearances for the Brig.
Manager Michael Clegg will be hoping to bolster his attacking options following their late 1-0 victory against newly-promoted Liversedge last weekend.
The two will go into contention for the Robins' next fixture where they will welcome South Shields to Greater Manchester.
Photo credit: Rotherham United & Accrington Stanley
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