Add multiple rows in a single row with different columns
You are on 10g, so PIVOT is unavailable, but still have the good old sum(case ...).

drop table reads purge;
drop table registers purge;

create table registers (id number,  n varchar2(2), prod_id number);
insert into registers values (331, '01', 112233);
insert into registers values (332, '02', 112233);
insert into registers values (333, '03', 112233);
insert into registers values (334, '04', 112233);
commit;

create table reads (read_id varchar2(3), register_id number);
insert into reads values ('011', 331);
insert into reads values ('012', 332);
commit;

SELECT
  sum(case when rg.n = '01' then rd.register_id end) as "RegisterID1",
  sum(case when rg.n = '02' then rd.register_id end) as "RegisterID2",
  sum(case when rg.n = '03' then rd.register_id end) as "RegisterID3",
  sum(case when rg.n = '04' then rd.register_id end) as "RegisterID4",
  count(rd.register_id) as "Count"
FROM Reads rd RIGHT JOIN Registers rg on rd.Register_ID = rg.ID
WHERE rg.Prod_ID = 112233;

RegisterID1 RegisterID2 RegisterID3 RegisterID4      Count
----------- ----------- ----------- ----------- ----------
        331         332                                  2