Julius Röntgen was a prolific and highly skilled Dutch-German composer with a dense, Brahmsian contrapuntal style. His ballade exhibits intellectual rigor combined with powerful Romantic expression.
Focus on the independence of the voices, specifically the dialogue between the inner melodic lines and bass.
Comparable difficulty and character — good candidates for what to learn next.
Ballade No.1 (Op.6) is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 8.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Ballade No.1 (Op.6) lasts about 7 minutes.
Ballade No.1 (Op.6) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Ballade in D moll by Julius Röntgen, Buiten by Julius Röntgen, Ballade by Samuel Coleridge-Taylor — see the full similar-pieces list on this page.