Royden/Roydon

meaning: 'hill where the rye grows' (Old English origin - ryge - 'rye' rygen- 'of rye' )
(named after a locality)
places; Roydon - in Essex, Norfolk, Suffolk.

The __den __don element means valley or bottom of a hillside

Other names are also after rye connections:
Royle (hill with rye, Lancs/Ches)
Ryall, Ryhall, Ryhill, Ryle, (hill where rye grows - Northd, East & West Yorks)
Rycott/Rycart - cottage in the rye (OE)
Rycraft/Rycroft - croft where rye grows (OE)
Rydell - valley where rye grows (eg Rydal in Lake District)
Ryland(s) - land/fields where rye grows (OE)

(from Basil Cottle - The Pengiun Dictionary of Surnames)

Royden/Roydon - Place Name evidence

Roydon Essex
Ruindune (Domesday Book),
Reidona c1130 (Calendar of Charters and Rolls in the Bodleian Library, Oxford pub 1878),
Reindon 1204,
Roindon 1208 Curia Regis Rolls

Roydon Norfolk near Diss
Rygedune c1035 Wills,
Regadona, Ragheduna Domesday Book,
Reydon 1242 The Book of Fees Rolls Ser. 1920-31

Roydon Norfolk, near Lynn
Reiduna Domesday Book,
Ridone 1254 The Valuation of Norwich ed. W.E.Lunt, Oxford 1926

Roydon Drift Suffolk near Long Melford
Rigen-, Rigindun c995 Cartularium saxonicum, ed Birch. London 1885-93

Meaning of all: 'Rye Hill'

The above list shows early occurances of the name in each area with the date and the document in which it appeared.

From The Concise Dictionary of English Place Names - Eilert Ekwall