The Collaborative International Dictionary of English v.0.48:

Roble \Ro"ble\, n. [Sp., oak.] (Bot.)
   The California white oak (Quercus lobata).
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Quercus lobata
    n 1: tall graceful deciduous California oak having leathery
         leaves and slender pointed acorns [syn: California white
         oak, valley oak, valley white oak, roble, Quercus
         lobata]