Hi Aiko,
My condolences to you and your family.
1) Must it be after 49 days?
>> Some people practice this, but not everyone. So it really depends on your family's beliefs. So long as it is within 100 days, it will be fine.
2) Can I have my ROM first then customary later? If this is the case does it mean that my customary have to be 3 years later?
>> Yes you can ROM first, no problem. Nowadays, people seldom practice the 3 years wait. Normally 1 year will suffice. This is a mark of respect for the deceased person. 3 years is too long...
3) Any other things that I need to take note of?
>> That will be all. Either you do it within 100 days or 1 year later (unless your family insist on the 3 years thingy...)
Hope this helps.