[syhprum (OP)]

I am continually bombarded by offers of free roulette spins, if I took $1000 and used it to make 1000 bets on either a single number or changed my number for each according to a list of random numbers how much would I have left after my 1000 bets

[RD]

...either a single number or changed my number for each according to a list of random numbers ...

Changing the number after each spin doesn't change the probability of winning:  as the roulette-wheel doesn't have a memory.
https://wikipedia.org/wiki/Gambler%27s_fallacy

if I took $1000 and used it to make 1000 bets on either a single number ... how much would I have left after my 1000 bets

The probability of winning is 1:37, but the house only pays-out 1:35 if you win.

So, on average, every 37 spins, (costing $37), you'd win $35 , i.e. net-loss of $2   

So, on average, your $1000 would become $946 , i.e. net-loss of $54

[ If someone is offering 1000 free bets there must be a catch somewhere ,
 e.g. that in exchange for the "free" bets they get your bank-account details, and help themselves to the contents ].

[syhprum (OP)]

I wrote a long reply then dropped the key board   ! thanks

[Bored chemist]

They usually won't let you cash out