Roca, 23, has established himself as a star player at the RCDE Stadium and was heavily linked with a move to Bayern Munich last summer.
His contract contains a €40m release clause and Arsenal are said to have held an interest in his signing since last summer, when they instead opted for the Ceballos deal.
A star at Under-21 level with Spain, it is widely thought that he will be a part of the senior national team in the coming years and he has started 24 league games for Espanyol this season.
However, his club remain at the foot of La Liga and the possibility of relegation is playing a part in clouding his future in Catalonia.