Can you apply for BG residence permit with Romanian residence permit?

Hmmm... for non-EU nationals, I think it's not so easy. Job offer is not enough.

Although pretty sure you don't need to return to Philippines for Type D, you should be able to get it at the Bulgarian Embassy in Bucharest.

My lawyer says the easiest way is as "trade representative". But this will cost a bit to setup.

How did you get your residence permit in Romania?

Also... bear in mind that in 3 years more years in RO, you should be eligible to get a EU Long Term Residence Permit. This will allow you freedom of movement within the EU, which means you could come to BG, or choose a higher paying country like Germany or Spain instead.

https://www.immigration2bulgaria.com/residence-permit/

*** TRO is one of the easyest options for obtaing residence permit in Bulgaria. So, the Labour agreement is also an option, but it requires some special conditions to meet, as a number of foreign workers in the company for example. If you have special educational and abilities you can apply for "blue card" permit, which is more interesting.

Hello! I got my residence thru an employer. I cannot stay here longer because my employer is leaving the country.

The Romanian RP gives you the right to enter Bulgaria despite all the restrictions. It is possible to apply to the nearest BG Consulate for Visa D if you meet all the requirements for RP.
***

You can apply in any consulate of Bulgaria (also in Romania) BUT you must have a valid reason for that. Such as employment as you suggested.