Starting rails. postgresql_adapter.rb FATAL - ruby-on-rails

Question

Hi I am new in Ruby on Rails.
I've installed Rails and everything was working fine.
Then I changed database from SQLite to Postgre (because Heroku don't support it),did git push to Heroku.Everything was fine.
But when I restarted my local repository,it showed me this(on local repo):
user~:$ rails server
=> Booting WEBrick
=> Rails 3.2.13 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:1215:in `initialize': FATAL: role "roma" does not exist (PG::ConnectionBad)
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:1215:in `new'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:1215:in `connect'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:323:in `initialize'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:27:in `new'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/postgresql_adapter.rb:27:in `postgresql_connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:315:in `new_connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:325:in `checkout_new_connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:247:in `block (2 levels) in checkout'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:242:in `loop'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:242:in `block in checkout'
from /usr/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:239:in `checkout'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:102:in `block in connection'
from /usr/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:101:in `connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_pool.rb:410:in `retrieve_connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_specification.rb:171:in `retrieve_connection'
from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/abstract/connection_specification.rb:145:in `connection'
from /usr/lib/ruby/vendor_ruby/active_record/railtie.rb:88:in `block in <class:Railtie>'
from /usr/lib/ruby/vendor_ruby/rails/initializable.rb:30:in `instance_exec'
from /usr/lib/ruby/vendor_ruby/rails/initializable.rb:30:in `run'
from /usr/lib/ruby/vendor_ruby/rails/initializable.rb:55:in `block in run_initializers'
from /usr/lib/ruby/vendor_ruby/rails/initializable.rb:54:in `each'
from /usr/lib/ruby/vendor_ruby/rails/initializable.rb:54:in `run_initializers'
from /usr/lib/ruby/vendor_ruby/rails/application.rb:136:in `initialize!'
from /usr/lib/ruby/vendor_ruby/rails/railtie/configurable.rb:30:in `method_missing'
from /home/roma/Templates/first_app/config/environment.rb:5:in `<top (required)>'
from /home/roma/Templates/first_app/config.ru:3:in `require'
from /home/roma/Templates/first_app/config.ru:3:in `block in <main>'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:55:in `instance_eval'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:55:in `initialize'
from /home/roma/Templates/first_app/config.ru:in `new'
from /home/roma/Templates/first_app/config.ru:in `<main>'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:49:in `eval'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:49:in `new_from_string'
from /usr/lib/ruby/vendor_ruby/rack/builder.rb:40:in `parse_file'
from /usr/lib/ruby/vendor_ruby/rack/server.rb:277:in `build_app_and_options_from_config'
from /usr/lib/ruby/vendor_ruby/rack/server.rb:199:in `app'
from /usr/lib/ruby/vendor_ruby/rails/commands/server.rb:46:in `app'
from /usr/lib/ruby/vendor_ruby/rack/server.rb:314:in `wrapped_app'
from /usr/lib/ruby/vendor_ruby/rack/server.rb:250:in `start'
from /usr/lib/ruby/vendor_ruby/rails/commands/server.rb:70:in `start'
from /usr/lib/ruby/vendor_ruby/rails/commands.rb:55:in `block in <top (required)>'
from /usr/lib/ruby/vendor_ruby/rails/commands.rb:50:in `tap'
from /usr/lib/ruby/vendor_ruby/rails/commands.rb:50:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
What can be cause of that?
Sorry for bad English.
In addition this is my database.yml file
development:
adapter: postgresql
database: my_database_development
pool: 5
timeout: 5000
test:
adapter: postgresql
database: my_database_development
pool: 5
timeout: 5000
production:
adapter: postgresql
database: my_database_development
pool: 5
timeout: 5000

Answer 1

Based on your error, you need to make a the user roma for your rails server to use to connect to your database. You can do this by using createuser to make your user defined in your database.yml. You may need to first do:
sudo su - postgres
createuser -P -s -e {your_machine_username}
but only if createuser throws an error with a normal createuser -P -s -e {user_defined_in_databaseyml}.
Then you can exit that user (exit will drop su) and do:
createuser -P -s -e {user_defined_in_databaseyml}
Then you should be able to rails s just fine (make sure you rake your db related tasks first).