Flask - (ProgrammingError) - Foreign key constraint when building postgresql database

I'm currently trying to deploy my flask application to Heroku, but I am encountering an error during database initialization.

Here is my models.py file:

from app import app  
from app import db  
from werkzeug.security import generate_password_hash, check_password_hash  
from sqlalchemy import create_engine, Column, Integer, String, Date, ForeignKey, event, Boolean, Table  
from sqlalchemy.orm import scoped_session, sessionmaker, backref, relationship  

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    password = db.Column(db.String(255), nullable=False, server_default='')
    email = db.Column(db.String(255), nullable=False, unique=True, index=True)
    confirmed_at = db.Column(db.DateTime())
    authenticated = db.Column(db.Boolean(), nullable=False, server_default='0')
    company_name = db.Column(db.String(100), nullable=False, server_default='')

    roles = db.relationship('Role')


    def __init__(self, email, company_name, password):
        self.email = email
        self.company_name = company_name
        self.set_password(password)

    def get_id(self):
        return self.email

    def is_active(self):
        #True, as all users are active.
        return True

    def is_authenticated(self):
        #"""Return True if the user is authenticated."""
        return self.authenticated

    def is_anonymous(self):
        #False, as anonymous users aren't supported."""
        return False

    def set_password(self, password):
        self.password = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password, password)

    def __repr__(self):
        return '<User %r>' % (self.company_name)

class Role(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100))
    user_id = db.Column(db.String, db.ForeignKey('user.id'))`

Here is my db_create.py file:

#!flask/bin/python
from migrate.versioning import api
from config import SQLALCHEMY_DATABASE_URI
from config import SQLALCHEMY_MIGRATE_REPO
from app import db
import os.path
db.create_all()
if not os.path.exists(SQLALCHEMY_MIGRATE_REPO):
    api.create(SQLALCHEMY_MIGRATE_REPO, 'database repository')
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
else:
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO, api.version(SQLALCHEMY_MIGRATE_REPO))

When initializing my database, I am receiving the following stack trace:

Traceback (most recent call last):
  File "db_create.py", line 7, in <module>
    db.create_all()
  File "/app/.heroku/python/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 895, in create_all
    self._execute_for_all_tables(app, bind, 'create_all')
  File "/app/.heroku/python/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 887, in _execute_for_all_tables
    op(bind=self.get_engine(app, bind), **extra)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 3404, in create_all
    tables=tables)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1616, in _run_visitor
    conn._run_visitor(visitorcallable, element, **kwargs)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1245, in _run_visitor
    **kwargs).traverse_single(element)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/visitors.py", line 120, in traverse_single
    return meth(obj, **kw)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/ddl.py", line 713, in visit_metadata
    self.traverse_single(table, create_ok=True)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/visitors.py", line 120, in traverse_single
    return meth(obj, **kw)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/ddl.py", line 732, in visit_table
    self.connection.execute(CreateTable(table))
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 729, in execute
    return meth(self, multiparams, params)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/sql/ddl.py", line 69, in _execute_on_connection
    return connection._execute_ddl(self, multiparams, params)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 783, in _execute_ddl
    compiled
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 958, in _execute_context
    context)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1159, in _handle_dbapi_exception
    exc_info
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 199, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 951, in _execute_context
    context)
  File "/app/.heroku/python/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 436, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (ProgrammingError) column "id" referenced in foreign key constraint does not exist
 '\nCREATE TABLE role (\n\tid SERIAL NOT NULL, \n\tname VARCHAR(100), \n\tuser_id VARCHAR, \n\tPRIMARY KEY (id), \n\tFOREIGN KEY(user_id) REFERENCES "user" (id)\n)\n\n' {}

Does anyone know what is causing this?

Thanks!