* Eight banks to arrange roadshows from Jan. 8 - statement* Perpetual dollar Tier 1 sukuk may follow* CEO said Oct. DIB needed capital boost after strong growth* Likely first Gulf bond deal of 2015(Adds details, background, data, context)DUBAI, Jan 6 (Reuters) - Dubai Islamic Bank DISB.DU said on Tuesday it picked eight banks to arrange roadshows from January 8 for a potential benchmark size dolla