B757-200 CREW HAD AN ALT UNDERSHOOT; AFTER THE CAPT CHANGED THE SID DEP IN THE FMC.

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DEP RWYS 25R AND 19L. I ANTICIPATED RWY 19L AND WE WERE CLRED THE TRALR DEP/DVC TRANSITION SO I ENTERED BOTH IN THE BOX FOR TKOF. THE CAPT ANTICIPATED RWY 25R AND CHANGED THE BOX. DURING PUSHBACK THE CTLR WANTED TO KNOW IF WE COULD ACCEPT RWY 19L FOR DEP. I RESPONDED YES AND THE CAPT REQUESTED THAT I CHANGE THE BOX TO REFLECT RWY 19L. I CHANGED THE PERFORMANCE INITIAL DATA TO REFLECT RWY 19L AND FOR SOME REASON; I WAS MOMENTARILY DISTR AFTER THAT AND FAILED TO CHANGE THE DEPS AND ARRS PAGE TO RWY 19L. NEITHER MYSELF NOR THE CAPT CAUGHT THIS ERROR AS THE PIT TWR WAS VERY BUSY AT THE TIME. AFTER TKOF; OUR INITIAL FIX (FIXIX) WAS NOWHERE TO BE FOUND AND MY FIRST PRIORITY WAS TO FLY THE PLANE. THE CAPT SCRAMBLED TO RETRIEVE OUR NAV DATA. I HAD FAMILIARIZED MYSELF WITH BOTH DEP PROCS AT THE GATE AND AS THE CAPT WORKED TO RE-ESTABLISH THE FIXES FOR RWY 19L; I PROCEEDED VFR AND I WAS SURE THAT MY LATERAL TRACK WAS CLOSE TO WHAT ATC EXPECTED. ROPPR INTXN IS COMMON TO BOTH RWYS 25R AND 19L PROCS AND REQUIRES A XING RESTR OF 7000 FT. CAPT NOTIFIED ATC THAT WE HAD AN FMC PROB AND ASKED TO PROCEED DIRECT TO ROPPR INTXN. WE WERE CLRED AS REQUESTED. PRIOR TO XING ROPPR ATC CLRED US TO CLB TO FL190 SO I CONTINUED TO CLB. WE CROSSED ROPPR SOMEWHERE BTWN 7000 FT AND 8000 FT AND HAD NOW ESTABLISHED OURSELVES ON COURSE. THERE WERE NO QUERIES FROM THE CTLR OR REQUEST TO CALL ATC; ETC. SUPPLEMENTAL INFO FROM ACN 612641: WE DEPARTED RWY 19L AND WHEN HE CALLED FOR LNAV; I NOTICED THE MAP DISPLAYED DATA FOR A RWY 25R DEP. THERE WAS A TIME OF CONFUSION AS I TRIED TO GET ORIENTED TO WHERE WE WERE SUPPOSED TO FLY. AT 7600 FT MSL; I CHALLENGED FO TO CHK ALT; REF: XING RESTR ANGLE OF BANK 7000 FT AT ROPPR INTXN. I AM CONCERNED ABOUT THE ALTDEV WITH REF TO THE XING RESTR.