02270. 00000 - "no matching unique or primary key for this column-list" For some reason I keep coming up with the 02270 error. However I'm not sure what's wrong with it. All I know is that the problem lies with the room table and the conferencesession table. 

CREATE TABLE BUILDING (
BUILDINGNO CHAR(2),
BUILDINGWING VARCHAR2(15),
BUILDINGLANE VARCHAR2(15),
CONSTRAINT BUILDING_PK PRIMARY KEY(BUILDINGNO));

CREATE TABLE SPEAKER (
SPEAKERID CHAR(2),
SPEAKERNAME VARCHAR2(20),
SPEAKERADDRESS VARCHAR2(50),
SPEAKERPHONE NUMBER(12),
CONSTRAINT SPEAKER_PK PRIMARY KEY (SPEAKERID));

CREATE TABLE ROOM (
BUILDINGNO CHAR(2),
ROOMNO CHAR(2),
ROOMCAPACITY NUMBER(3),
CONSTRAINT ROOM_PK PRIMARY KEY(ROOMNO,BUILDINGNO),
CONSTRAINT ROOM_FK1 FOREIGN KEY(BUILDINGNO)REFERENCES BUILDING(BUILDINGNO));

CREATE TABLE CONFERENCESESSION (
SESSIONID CHAR(4),
BUILDINGNO CHAR(2),
ROOMNO CHAR(2),
SPEAKERID CHAR(2),
SESSIONDATE DATE,
SESSIONPRICE NUMBER(4,2),
CONSTRAINT CONFERENCESESSION_PK PRIMARY KEY(SESSIONID),
CONSTRAINT CONFERENCESESSION_FK1 FOREIGN KEY(BUILDINGNO) REFERENCES 
BUILDING(BUILDINGNO),
CONSTRAINT CONFERENCESESSION_FK2 FOREIGN KEY(ROOMNO) REFERENCES ROOM(ROOMNO),
CONSTRAINT CONFERENCESESSION_FK3 FOREIGN KEY(SPEAKERID) REFERENCES 
SPEAKER(SPEAKERID));
This:

CREATE TABLE CONFERENCESESSION (
SESSIONID CHAR(4),
BUILDINGNO CHAR(2),
ROOMNO CHAR(2),
SPEAKERID CHAR(2),
SESSIONDATE DATE,
SESSIONPRICE NUMBER(4,2),
CONSTRAINT CONFERENCESESSION_PK PRIMARY KEY(SESSIONID),
CONSTRAINT CONFERENCESESSION_FK1 FOREIGN KEY(BUILDINGNO) REFERENCES 
BUILDING(BUILDINGNO),
CONSTRAINT CONFERENCESESSION_FK2 FOREIGN KEY(ROOMNO) REFERENCES ROOM(ROOMNO),
CONSTRAINT CONFERENCESESSION_FK3 FOREIGN KEY(SPEAKERID) REFERENCES 
SPEAKER(SPEAKERID));


Should be changed to:

CREATE TABLE CONFERENCESESSION (
SESSIONID CHAR(4),
BUILDINGNO CHAR(2),
ROOMNO CHAR(2),
SPEAKERID CHAR(2),
SESSIONDATE DATE,
SESSIONPRICE NUMBER(4,2),
CONSTRAINT CONFERENCESESSION_PK PRIMARY KEY(SESSIONID),
CONSTRAINT CONFERENCESESSION_FK1 FOREIGN KEY(BUILDINGNO, ROOMNO) REFERENCES 
ROOM(BUILDINGNO, ROOMNO),
CONSTRAINT CONFERENCESESSION_FK2 FOREIGN KEY(SPEAKERID) REFERENCES 
SPEAKER(SPEAKERID));


A foreign key requires a unique or primary key constraint on the referenced columns in the parent table. A multi-column constraint is not interchangable with single-column constraints.