I am an Indian citizen married to a Romanian woman. We have a two-month-old child. I have been living in Romania for the last 6 and a half months. I have a Temporary Residence Permit from Romanian authorities. Now we would like to relocate to London together to find work and settle. My wife and son don't need a visa to enter and remain in the United Kingdom. Can I enter the UK with my residence permit or do I need some kind of visa? If I do need a visa, which visa do I need and how do I apply?
You should apply for an EEA family permit.
When you apply, be careful to include the fact that you and your wife have a child together. There is apparently a strong tendency for applications to be refused because the entry clearance officer (ECO) suspects a marriage of convenience.
The UK's own guidance to ECOs explicitly says that couples who have children together must not be suspected of having a marriage of convenience, so this is your best strategy to avoid a refusal.
Once you arrive in the UK, you will need to apply for a residence card as evidence of your continued right to live there.