FLT CREW OF B737 ON SHEAD RNAV DEP FROM LAS FAIL TO MEET 7000 FT OR BELOW RESTR AT ROPPR WAYPOINT WHEN ATC CLRED THEM TO FL190 JUST AS THEY WERE LEVELING OFF.

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CHAIN OF EVENTS: FLT XXXX FROM LAS. RECEIVED CLRNC OF COMPANY FLT NUMBER CLRED VIA THE SHEAD ONE DEP SQUAWK XYZW. ALL RNAV PRE-DEP PROCS WERE FOLLOWED. RWY POS UPDATE; TOGA SELECTED. THE INITIAL 7000 FT RESTR AT ROPPR WAS SET IN ALT WINDOW. WX AT DEP WAS 5000 FT BROKEN 6000 FT OVCST VISIBILITY 7 MI LIGHT RAIN. DEPARTED RWY 19L (LAS). TKOF WAS NORMAL. LNAV ENGAGED AT 500 FT AGL. LEVEL CHANGE AT 800 FT AGL AUTOPLT AT 1000 FT AGL. FLAPS RETRACTED PER SCHEDULE. ENTERED IMC CONDITIONS AT 5000 FT. LIGHT TURB MODERATE RAIN. INITIAL CLB AT 220 KIAS. ACFT TURNED NORMALLY AT FIXIX TOWARD ROPPR. AT APPROX 3 MI PAST FIXIX (PASSING 6000 FT) AUTOPLT ACQUIRED THE 7000 FT ALT AND STARTED REDUCING PITCH TO CAPTURE 7000 FT. (RATE OF CLB APPROX 2550 FPM.) ACCELERATING THROUGH 230 KTS; I STARTED REDUCING PWR (AT APPROX 6500 FT). SIMULTANEOUSLY WITH THE AUTOPLT LEVELOFF; WE RECEIVED A NEW CLRNC FROM DEP; 'CLB AND MAINTAIN FL190.' PNF SET FL190 IN THE ALT WINDOW; WHICH NEGATED THE LEVELOFF CAPABILITY OF THE AUTOPLT. WE THEN HEARD AN ADDITION TO THE CLRNC; 'COMPLY WITH RESTRS.' (ALL THIS HAPPENED WITHIN 5-10 SECONDS.) WHEN I HEARD THE CLB TO FL190; I BEGAN TO ADD PWR TO CONTINUE THE CLB AND I HEARD THE COMPLY WITH RESTRS PART OF THE CLRNC PASSING APPROX 7200 FT. I BEGAN A GENTLE NOSE OVER AT 7500 FT AND THE ACFT REACHED 7800 FT BEFORE DSNDING. ALL THE WHILE; I WAS REDUCING PWR. RATE OF CLB AT THE 7200 FT POINT WAS APPROX 2300 FPM. AS WE DSNDED; PNF RESET 7000 FT IN THE ALT WINDOW. WE CROSSED ROPPR AT 7000 FT AND THEN CONTINUED TO CLB TO MAKE SUBSEQUENT RESTRS ON THE DEP. THE CONFUSION AND SUBSEQUENT ALTDEV OCCURRED BECAUSE OF THE WAY THE CLRNC WAS GIVEN; THE TIMING OF THE NEW CLRNC (WHICH OCCURRED BEFORE A CRITICAL LEVELOFF POINT) AND THE NORMAL PROC TO SET THE ALT CLRED TO IN THE WINDOW. IN THE FUTURE; I WILL NO LONGER CHANGE THE ALT WINDOW UNTIL THE COMPLETE CLRNC IS RECEIVED AND UNDERSTOOD. I THINK A BETTER WAY OF ISSUING THIS TYPE OF CLRNC WOULD BE; 'CLB VIA THE SHEAD ONE DEP PROFILE EXCEPT TO MAINTAIN FL190.' THIS WOULD ENSURE THE IMPORTANCE OF FOLLOWING THE PROFILE INSTEAD OF JUST CLBING OUT OF THE TERMINAL AREA. IT ALSO WOULD 'CLOSELY' MIRROR THE PHRASEOLOGY USED DURING ARRS. 'DSND TO CROSS LYNSY AT 12000 FT; THEN DSND PER THE LYNSY ARR' -- EXAMPLE. SUPPLEMENTAL INFO FROM ACN 599256: SOME THINGS THAT CONTRIBUTED ARE: RECEIVING A CLRNC TO CLB DURING A LEVELOFF AND AT A BUSY TIME MAY HAVE CAUSED SOME CONFUSION. I MEAN WE WERE CLRED TO CLB AND REQUIRED TO LEVELOFF AT THE SAME TIME. WE NATURALLY DID NOT WANT TO BE IN THE ROUGH AIR AND RAIN; THEREFORE; WE WANTED TO HEAR A CLRNC THAT WOULD MOVE US OUT OF THE WX. SOME THINGS THAT COULD BE DONE TO HELP AVOID THE SIT: CREWS SHOULD UNDERSTAND THE CLRNC BEFORE THEY CHANGE THE WINDOW. ACTIVATE VNAV. CHANGE THE CLRNC PROC. HAVE CLRNC DELIVERY ISSUE THE FL190 AMENDMENT TO THE SID; IE; '...CLB VIA THE SHEAD RNAV ONE DEP PROFILE TO MAINTAIN FL190; EXPECT FILED ALT 10 MINS AFTER DEP. SQUAWK...'. MY CLRNC WAS 'COMPANY FLT NUMBER IS CLRED TO XXX VIA THE SHEAD ONE DEP AS FILED. SQUAWK XYZW.' OUR FILED ALT WAS FL280. WAIT UNTIL THE DEPARTING ACFT IS ESTABLISHED ON THE CLB PROFILE TO AMEND THE CLRNC. IT SEEMS LIKE THE MOST RESTRICTIVE AND IMPORTANT PART OF THE CLRNC IS TO MAINTAIN THE PROFILE CLB. SO PERHAPS THE CLRNC SHOULD START WITH; 'CLB ON THE SHEAD ONE DEP PROFILE TO MAINTAIN FL190.' ISSUE THE AMENDED CLRNC USING TERMINOLOGY SIMILAR TO THE RNAV ARRS; '...CONTINUE CLB VIA THE SHEAD RNAV ONE DEP TO MAINTAIN FL190.' THE CLRNC 'CLB AND MAINTAIN FL190; COMPLY WITH RESTRS;' IS NOT VALID BECAUSE ONE OF THE RESTRS IS TO CROSS BIKKR AT OR ABOVE FL250. BECAUSE THE LAS SID/STAR TERMINAL PROCS ARE CONTINUING TO EVOLVE; I WILL BE EVEN MORE CAREFUL TO REMAIN ON THE ESTABLISHED CLRNC UNTIL I CLRLY UNDERSTAND ANY CLRNC AMENDMENT OR CHANGE. I APOLOGIZE FOR THE PROBS CAUSED BY MY MISTAKE. CALLBACK CONVERSATION WITH RPTR ACN 598979 REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT THIS INCIDENT WAS ONE OF SEVERAL THAT OCCURRED ONTHE FIRST FEW DAYS OF EFFECTIVITY OF THIS DEP. SUBSEQUENT DEPS SEEM TO HAVE MODIFIED THE PHRASEOLOGY USED BY CTLRS. HIS INTERVIEW WITH L30 TRACON INCLUDED DISCUSSION REGARDING THE LACK OF AN ACTIVE VNAV FUNCTION ON HIS CARRIER'S FMS EQUIPPED ACFT. THE LACK OF THE VNAV FUNCTION REMOVES ONE BACK-UP POSSIBILITY IN THAT ACFT SO EQUIPPED WILL LEVEL AT THE WAYPOINT RESTR EVEN IF THE ALT WINDOW IS SET HIGHER; UNTIL SUCH TIME AS THE RESTR ITSELF IS ERASED FROM THE LEGS PAGE OF THE FMS. WHILE THIS IS TRUE; THE FACT BEGS THE QUESTION OF WHETHER THE PHRASEOLOGY EMPLOYED BY ATC COULD AND HAS BEEN INTERPED IN THE COCKPIT AS A DELETION OF THE INITIAL ALT RESTR; THE 7000 FT OR BELOW DIRECTION AT ROPPR WAYPOINT.