Wanting to Open a Roth IRA.. Confused about the process

I have an individual brokerage account and work a government job that will pay out for life once I hit a certain age. I'm wanting to open an individual roth IRA. My brokerage account is through TD Ameritrade, so I was thinking due to the merge, for simplicities sake to open it through Schwab. If I open a Roth IRA through Schwab, when the merge happens will my Roth and brokerage account combine so I only have one login (and can view my roth and brokerage account), or will each account have a separate login? Do you reccomend schwab? I know very little about tax free accounts. Thanks.